HYPOTHESIS AND THEORY ARTICLE
published: 31 October 2013
doi: 10.3389/fpsyg.2013.00746
Why are dreams interesting for philosophers?
The example of minimal phenomenal selfhood, plus an
agenda for future research1
Thomas Metzinger 1,2*
1
2
Philosophisches Seminar, Johannes Gutenberg-Universität, Mainz, Germany
Frankfurt Institute for Advanced Studies, Frankfurt am Main, Germany
Edited by:
Jennifer M. Windt, Johannes
Gutenberg-Universität, Germany
Reviewed by:
Sebastian Dieguez, Université de
Fribourg, Switzerland
Philip Gerrans, University of
Adelaide, Australia
*Correspondence:
Thomas Metzinger, Philosophisches
Seminar, Johannes
Gutenberg-Universität Mainz,
Jakob-Welder-Weg 18, D-55099
Mainz, Germany
e-mail: metzinger@uni-mainz.de
This metatheoretical paper develops a list of new research targets by exploring
particularly promising interdisciplinary contact points between empirical dream research
and philosophy of mind. The central example is the MPS-problem. It is constituted by
the epistemic goal of conceptually isolating and empirically grounding the phenomenal
property of “minimal phenomenal selfhood,” which refers to the simplest form of
self-consciousness. In order to precisely describe MPS, one must focus on those
conditions that are not only causally enabling, but strictly necessary to bring it
into existence. This contribution argues that research on bodiless dreams, asomatic
out-of-body experiences, and full-body illusions has the potential to make decisive future
contributions. Further items on the proposed list of novel research targets include
differentiating the concept of a “first-person perspective” on the subcognitive level;
investigating relevant phenomenological and neurofunctional commonalities between
mind-wandering and dreaming; comparing the functional depth of embodiment across
dream and wake states; and demonstrating that the conceptual consequences of cognitive
corruption and systematic rationality deficits in the dream state are much more serious for
philosophical epistemology (and, perhaps, the methodology of dream research itself) than
commonly assumed. The paper closes by specifying a list of potentially innovative research
goals that could serve to establish a stronger connection between dream research and
philosophy of mind.
Keywords: consciousness, self-consciousness, minimal phenomenal selfhood, full-body illusions, out-of-body
experiences, bodiless dreams, first-person perspective, mind wandering
THE RELEVANCE OF DREAM RESEARCH FOR PHILOSOPHY
OF MIND—AND VICE VERSA
This paper has two parts. First, I will develop an answer to the
problem of how to isolate the property of “minimal phenomenal selfhood” (MPS; cf. Blanke and Metzinger, 2009), that is, the
simplest form of self-consciousness. Part 1 is also a case study,
presenting a specific example to make a more general point. I
want to show how dream research can make a decisive contribution to the philosophical project of conceptually describing
the deepest and functionally fundamental layers of human selfconsciousness, and in a way that can turn them into proper
explananda for empirical research programs. Part 2 will formulate
a short research agenda for future cooperation between philosophy of mind and empirical dream research. My goal in this
second part is to develop a short, non-exclusive list of particularly promising contact points, in order to demonstrate why and
where exactly a much denser cooperation between the two fields
would accelerate progress on both sides. From this discussion
1I
want to thank Jennifer Windt, both reviewers, Adrian Alsmith, and Susan
Blackmore for helpful discussion and important pointers to relevant literature.
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I will extract a catalogue of desiderata, i.e., a list of the most
promising targets for future research.
How do we acquire knowledge about the world? Is it possible
to demonstrate the existence of a mind-independent, external world beyond the contents of subjective experience? For
centuries, philosophers have debated the reliability of sensory
experience, searching for criteria allowing us to distinguish
between waking and dreaming, and confronted the challenge of
dream scepticism: Could all of this be a dream, including all of my
empirical and sensory-based knowledge? As we might in principle
be deceived not merely about external reality, but also about our
own minds, dreaming not only poses questions for epistemology,
but also for the philosophy of mind and consciousness. A central
methodological concern shared by philosophers and empirical
psychologists alike is the status of first-person reports, for example as gathered from sleep laboratories (cf. Windt, 2013): How
reliable are they, and are there really “first-person data” in a literal
sense that could be taken at face value, directly entering the process of scientific theory formation? During the last three decades,
research on the problem of conscious experience has emerged as a
field of systematic, rigorous research in its own right (Metzinger,
1995, 2000; Seth, 2007). Here, dreaming is an important contrast
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condition for theories of waking consciousness and perhaps
it could even serve as a global model of conscious experience
in the future, as it presents us with a second global state of
consciousness aside from wakefulness (Revonsuo, 2006, 2010).
A slightly more modest approach would be a contrastive analysis
(Windt and Noreika, 2011), which only focuses on specific
aspects of oneiric phenomenology, comparing them to ordinary,
pathological, or certain altered states of waking consciousness
without yet assuming a complete theory of dream consciousness.
Today, the phenomenon of dreaming has not only become one
of the most interesting objects of study at the interface between
philosophy of mind and empirical research programs, but a
genuine research tool in itself. One hope is to use dreams as an
instrument that guides researchers to a deeper understanding of
consciousness, self-consciousness, and subjectivity.
PART 1
WHAT IS THE MPS-PROBLEM?
The MPS-problem is one small and well-defined - but potentially
decisive - aspect of the problem of consciousness. Its methodological relevance consists in a simple, but important fact: Minimal
phenomenal selfhood is the absolutely central and necessary
starting point for any conceptually systematic and empirically
rigorous research program confronting the subjectivity of consciousness. The problem of consciousness is not one problem, but
a whole bundle of problems (see Metzinger, 1995, 2000, 20102 for
introduction). Some of these problems are metatheoretical, for
example:
• What counts as an explanation?
• What is the proper conceptual interpretation of psychophysical
correlations?
• What is the epistemological status of first-person reports?
• Are there methodological constraints on the use of autophenomenological reports in experimental design?
• (. . .)
Other problems are empirical, such as:
• What is the minimally sufficient neural correlate of consciousness?
• What are the functional differences characterizing conscious vs.
unconscious information processing?
• If the NCC has been isolated, and if we have a satisfactory computational model of its activity, is there something that could be
specified as the overarching “computational goal” of conscious
experience in individual organisms?
• In an evolutionary context, was there an adaptive function
of consciousness, did conscious processing maximize inclusive
fitness?
• (. . .)
There are many more of such sub-problems. They are all important, and together they constitute a cluster of research targets that
today we call “the problem of consciousness.” However, at least
from a philosophical point of view, there clearly is something
like a core issue: What exactly is a “first-person perspective”
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Why are dreams interesting for philosophers?
(1PP; Box 1)? What do we mean by saying that consciousness is
“subjective”, for example when developing anti-reductionist and
anti-naturalist arguments trying to show that an empirical explanation of consciousness is out of reach (for classical examples see
Nagel, 1974; Jackson, 1982; Levine, 1983)?
I believe that the 1PP can be naturalized, because it is a naturally evolved epistemic modality, a highly specific representational
format creating an internal mode of presenting knowledge and
information in the brain of a conscious organism. In order to
understand what a 1PP is, we must understand what a phenomenal self is. And in order to understand what a phenomenal self
really is, we must begin by isolating the minimal version of our
target phenomenon. We must first focus on those conditions that
are not only causally enabling, but strictly necessary to bring it into
existence.
Why is this strategy advisable? Human self-consciousness is
an extremely complex target phenomenon: It is socially, historically and culturally embedded; it has personal and subpersonal
functional layers; some of its representational contents are nonconceptual, while others are conceptual or propositional; some
content layers are phenomenally transparent while others are phenomenally opaque2 ; all of these layers dynamically interact; there
are different levels of embodiment and grounding (Metzinger,
2014); and so on. Therefore, I propose to adopt a heuristic principle, the principle of “explanatory parsimony”: At least at the
outset, we should minimize the number of qualitative kinds or
types of self-consciousness that we try to explain scientifically or
that, as naturalistic philosophers, we try to isolate conceptually as empirically tractable entities in the first place. Minimal
self-consciousness is an experience that does not have proper
parts that could themselves count as a kind or type of selfconsciousness. “Explanatory parsimony” simply means that in an
extremely complex domain, we must begin by focusing on strictly
necessary constituents. We must first ask what the minimal form
of our target phenomenon actually is. And it is at this point that
dream research becomes relevant to philosophy of mind.
MINIMALITY AND THE PHENOMENOLOGY OF
IDENTIFICATION
What is the simplest form of self-consciousness, both in dreaming, and in waking? What is the minimal “phenomenal selfmodel” (PSM; Metzinger, 2003a, 2007; Blanke and Metzinger,
2009), or the minimal global system model that allows a given
conscious system to experience itself as a single and distinct
autonomous entity, as a self (Limanowski and Blankenburg,
2013)? What, functionally speaking, constitutes such an internal
model? “Single” means that a system represents itself as a unified,
2 “Transparency” is a property of conscious representations, namely, that
they are not experienced as representations. Therefore, the subject of experience feels as if being in direct and immediate contact with their content.
Transparent conscious representations create the phenomenology of naïve
realism (see next footnote and the references given there). An opaque phenomenal representation is one that is experienced as a representation, for
example in pseudo-hallucinations or lucid dreams. There exists a graded
spectrum between transparency and opacity, determining the variable phenomenology of “mind-independence” or “realness.” Unconscious representations are neither transparent nor opaque.
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countable individual, possessing numerical identity. “Singularity,”
defined in terms of “unification” and “indivisibility,” implies that
some sort of integration has taken place. Therefore, we must
look for all those functions in the brain that (a) contribute to
global self-representation, and (b) dynamically integrate information and representational contents from more than one source,
while (if we also want minimality) (c) none of those contents
can themselves be taken to be a representation of the system as a
whole. “Distinctness” means that, necessarily, a self/world boundary exists. Normally this will include the additional representation
of a structured environment involving other unified, countable
individuals. One related phenomenological constraint is that we
experience ourselves as parts of the world, so we must look for
those neurally realized functions that seamlessly embed the selfmodel into a given multimodal scene or situation. And saying
that a system treats itself as an “entity” means that it must have
attributed a specific ontological status to itself: It experiences itself
as existing. However, the phenomenology of existence—of the
“realness” of the self—has nothing to do with the self-attribution
of some property in a linguistic, conceptual, or cognitive sense. It
is a pre-reflexive aspect of subjective experience3 .
MINIMAL PHENOMENAL SELFHOOD: THE ORIGINAL
HYPOTHESIS
In 2009, Blanke and Metzinger introduced the concept of
“minimal phenomenal selfhood” (MPS). MPS can be analyzed
on phenomenological, representational, and functional levels of
description. Central defining features are (1) a globalized form
of identification with the body as a whole (as opposed to ownership for body parts), (2) spatiotemporal self-location, and (3) a
1PP. It is important to differentiate between a weak and at least
two stronger readings of the term “1PP.” A weak 1PP is a purely
geometrical feature of a perceptual or imagined model of reality and has formed the target of empirical studies investigating
visuospatial perspective-taking (see, e.g., Pfeiffer et al., 2013). For
example, in the human case a unimodal (e.g., visual) weak 1PP
typically includes an egocentric spatial frame of reference, plus a
global body representation, with a perspective originating within
this body representation. There is a center of projection that functions as the geometrical origin of the “seeing” organism’s passive
perspective.
MPS is the central enabling condition for having a subjective, consciously experienced 1PP on the weak reading; it is a
3 The
phenomenology of “realness” can be analyzed as the phenomenal transparency of certain conscious representations, i.e. as the fact that the system
has no introspective access to non-intentional properties of its own representations, that it is necessarily unaware of the construction process (see
Metzinger, 2003a: 3.2.7 and Metzinger, 2003b: 354pp for details). If we move
from the representationalist to the functionalist level of analysis, we may interpret experiential “realness” as the Bayes-optimality or dynamical stability of
the generative models employed. On this level, my claim would be that the
origin of the 1PP (the minimal phenomenal self) is not tied to a specific form
of content, but to the region of maximal invariance, that is, to the most robust,
dynamically stable, and Bayes-optimal region in the overall model of reality.
There is a “gradient of realness,” and the most real (or “phenomenally transparent”) partition of the conscious model of the world is the aspect which
minimizes prediction error most reliably; cf. Limanowski and Blankenburg
(2013).
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Why are dreams interesting for philosophers?
necessary (but not sufficient) condition on two stronger readings of the term “1PP”4 . Having MPS is a necessary condition
for the strong (i.e., attentional and/or cognitive) 1PP, but not for
the weak 1PP, because the weak 1PP is itself a constituting factor for MPS. The notion of “embodiment” is of central relevance
for MPS, as is the question of how critical global bodily properties like self-identification, self-location and 1PP can be grounded
and functionally anchored in the brain (Metzinger, 2014). In standard configurations, the conscious body-model defines a volume
within a spatial frame of reference (the dimension of “selflocation”) within which the geometrical origin of the weak 1PP
is also localized. Self-location possesses a variable internal structure: the bodily self is phenomenally represented as inhabiting a
volume in space, whereas the weak 1PP is projected from an extensionless point, the geometrical origin of our perspectival visual
model of reality. Normally this point of origin is embedded within
the volume defined by bodily self-representation (though it can
be dissociated).5 Because our conscious body model is transparent, that is, because it cannot introspectively be recognized as
a model, we fully identify with its representational content and
enjoy the phenomenology of presence as real, distinct, unified and
individual bodily selves.
DIFFICULTY 1: INDETERMINACY OF THE OBJECT OF IDENTIFICATION
In an important criticism, Adrian Alsmith has argued that a set
of classical studies on the experimental induction of “full-body
illusions” (FBIs; see Blanke, 2012 for review) are basically a misnomer. His point is that the possibility has not been excluded that
they only create a partial identification with the avatar used as
an alternative, second body-representation in these experiments.
Alsmith (né Smith) writes:
Unfortunately, the question of whether or not there are full-body
illusions is empirically under-determined, as putative full-body
illusions are difficult to isolate from illusions involving composite parts that to do constitute a “full” or “whole” body. That is
to say, a plausible alternative is that only representations of the
body parts directly stimulated become subject to the experimentally induced bias, whilst other parts remain relatively (perhaps
even completely) unaffected. (. . .)
The difficulty is that there is little assurance that this is a manipulation of a global representational process. In particular, the issue
4 An even stronger 1PP emerges if a system represents itself as an epistemic
agent, that is, as a system that actively seeks to expand or improve its knowledge about the world (Box 1). Two major ways in which this can be done
is, first, by optimizing the precision of its perceptual model of the world via
the selective control of attentional mechanisms and active sampling (“attentional agency”, AA, see section Example 1: The Concept of a “first-person
perspective”), or second, by forming new concepts and abstract representations of reality (“cognitive agency”). A strong 1PP occurs when the model of
the organism as a whole, given through MPS, is represented as being directed
at an object component (including, potentially, the body itself). A cognitive
1PP appears when a system possesses an abstract concept of itself as a subject
of experience, and is able to apply this concept to itself. See Metzinger, 2003a,
2006, 2007 for details.
5 I have called this the “embedding principle.” For empirical examples demonstrating how both aspects can be functionally dissociated, suspending the
embedding principle, see De Ridder et al., 2007; Ehrsson, 2007; Lenggenhager
et al., 2007.
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arises because there is no measure of the extent to which the effect
is localized to particular parts. For claiming that the illusion is
a full-body illusion surely involves the assumption that it is not
localized to particular parts (Smith, 2010, p. 38p).
First, to avoid potential conceptual confusions, let us differentiate the issue of empirical under determination of the existence
of FBIs and the phenomenal indeterminacy of the object of identification. The latter might or might not underlie the first. One
important distinction is the one between local and global ownership (Blanke and Metzinger, 2009: 9; Petkova et al., 2011; for
a useful discussion see Lenggenhager, 2009, section 4.2.3). For
example, in a disorder that has been called somatoparaphrenia,
the phenomenology of ownership for a body part may break
down following damage to right temporo-parietal cortex (Vallar
and Ronchi, 2009). Somatoparaphrenic patients most often misattribute their contralesional hand as belonging to another mostly
familiar person such as their doctor, nurse, a hospital neighbor, or friend. Somatoparaphrenia must be distinguished from
other bodily symptoms reflecting disturbed partial ownership
and/or agency such as xenomelia (the persistent desire for healthy
limb amputation, caused by the oppressive feeling that one or
more limbs of one’s body do not belong to one’s self, formerly
labeled “body integrity identity disorder” or BIID, McGeoch et al.,
2011; Brugger et al., 2013; Hilti et al., 2013; van Dijk et al.,
2013), anosognosia for a paralyzed limb, alien hand syndrome,
depersonalization disorder, congenital and supernumerary phantom limbs, or selective loss of the visual body-representation
(as in asomatoscopia, negative heautoscopy, see Dieguez and
Blanke, 2011; Dieguez and Annoni, 2013). If one takes reports
of these symptoms seriously and uses them to develop a set of
heterophenomenological constraints6 for any satisfactory theory
underlying human self-consciousness, in particular of the identification component, one immediately begins to see the complexity of our high-dimensional, variable inner landscape of bodily
self-consciousness. Alsmith’s point about the potential empirical
under determination of bodily self-identification has only been
empirically demonstrated for local patterns of identification relating to the experience of single fingers during the rubber hand
illusion (Tsakiris and Haggard, 2005; Tsakiris et al., 2006, p. 427).
But it might even be possible that there is no empirical fact of the
matter, as there is a deeper underlying problem, namely, the possibility of phenomenal indeterminacy. This would mean that the
distinction between global and local body ownership is not given
in phenomenal experience itself and is only an artifact of our
way of describing it. However, at the very least, Alsmith’s argument certainly implies that relevant phenomenological aspects
like “identification” and “ownership” cannot be captured by a
6 Heterophenomenological
constraints are third-person constraints for a scientific theory of subjective experience, exclusively based on the reports people
give about their own experience, and not on some dubious form of direct
access to “the experience itself.” Daniel Dennett (2003, p. 20) claims “The
total set of details of heterophenomenology, plus all the data we can gather
about concurrent events in the brains of subjects and in the surrounding
environment, comprise the total data set for a theory of human consciousness. It leaves out no objective phenomena and no subjective phenomena of
consciousness.”
Frontiers in Psychology | Consciousness Research
Why are dreams interesting for philosophers?
simple global/local distinction, but have to be described in their
fine-grained variance over time (Longo et al., 2008; Tsakiris, 2010;
Longo and Haggard, 2012). And this leads to an interesting new
version of our central question: What exactly is the minimal unit
of identification?
DIFFICULTY 2: DOES THE DISTINCTION BETWEEN
SELF-IDENTIFICATION AND SELF-LOCATION COLLAPSE?
There are two classes of phenomenal states in which we find
a robust, temporally stable form of self-consciousness in the
absence of an extended body representation: “asomatic” out-ofbody experiences (OBEs) and “bodiless” dreams. These stateclasses are highly relevant, because they help us refine the
theoretical constraints for a more comprehensive theory of selfconsciousness, and, more simply, because they demonstrate a
possibility that any such theory would have to explain.
Asomatic OBEs
Out-of-body experiences are episodes of phenomenal consciousness during which subjects experience themselves as being located
outside of their physical bodies, often (but not necessarily) involving a perceptually impossible external perspective from which the
physical body is seen, heard, or felt. An “asomatic” OBE is one
in which the experiential subject lacks any spatial form, because
it is phenomenologically identified with an extensionless point in
space, external to the physical body as represented (Green, 1968:
17; Irwin, 1985: 8p; Box 2). “Parasomatic” OBEs are characterized by the subjective experience of being embodied in a spatial
volume. This can involve phenomenologically either identifying
with a double body, which may share many of the features of
the physical body as visually represented, or with an indeterminate form, but again external to the physical body as represented.
“Aparasomatic” OBEs are a third phenomenological category, in
which some sort of counterpart of the experient’s physical body is
actually represented alongside the physical body, but in which the
subject neither identifies with the double nor the physical body as
phenomenally represented. For example, a German study found
18.8 % of subjects describing their OBEs as bodiless, with 34.4%
perceiving themselves as “being located in a body resembling my
own physical body” and 21.9% found themselves “in a cloud, fog,
or at a point in space” (Wolfradt, 2000/2001; English translation
TM). Depending on the study (see Alvarado, 2000 for a comprehensive review), at least a third of the subjects find themselves
located in a second body (but this may also be an indefinite spatial
volume) and, on average, about 31 percent of OBEs are actually
asomatic—they are experienced as bodiless and often include an
externalized visuospatial perspective only.7 However, the object
7 As Alvarado (1997, p. 16) remarks, little systematic work has been conducted
on the phenomenology of the experience (see also Alvarado, 1986, 2000, p.
186). In autoscopy, the object-component of the first-person perspective—
what the subject is phenomenally directed at—is formed by a self-model which
is not a subject-model, it is not a representation of a knowing self. You see your
own body, and you recognize it as your own, but presently it is not the body
as subject, the body as the locus of knowledge and of lived, conscious experience –there are two bodies, but only one EAM. The phenomenal “ownership”
for the physical body is based on instant recognition only, but not on identification. Only one of the currently active self-models functions as the “locus of
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of identification can also change in the course of one single conscious episode; for example, an asomatic OBE might gradually
be transformed into a parasomatic OBE, etc. Carlos Alvarado
writes:
Some experience being in another body, usually resembling their
physical one (n = 10 studies; M = 46%, Mdn = 49%; range =
15–75%). Others do not experience a body at all, describing themselves as “pure consciousness” (n = 6 studies; M = 31%: Mdn. =
21.5%; range = 7–80%) or as “balls of light,” “points in space,” or
“clouds” (n = 6 studies; M = 29%; Mdn 28%; range = 13–47%).
(Alvarado, 2000, p. 186p).
The most important conceptual implication is that we have not
only a plausible candidate for the minimal unit of identification (see section Difficulty 1: Indeterminacy of the Object of
Identification. above), but also a candidate for what I would like to
call the maximal unit of identification (Box 2). What is the “maximal unit of identification”? It is the possibility of identifying with
the most general phenomenal property available for identification
at all: Philosophers might call it the global “unity of consciousness,” or phenomenality per se, or awareness as such, namely the
singular, integrated, all-pervading quality of consciousness characterizing the current totality of experiential contents, as it is
given in every single moment of experience.
Here, the first general insight is that the identification component of phenomenal self-consciousness can in principle be
attached to a whole range of different phenomenal properties.
It follows that there must be a neural mechanism underlying the phenomenology of identification. It is also plausible to
assume that the function implemented by this mechanism is
domain-general, because it can operate on a variety of representational contents and/or phenomenal properties. Call this the
“UI-theory”: Conscious experience can be described as a trajectory through a high-dimensional state space; in navigating
the world and orienting themselves, human beings constantly
search for a source of maximal invariance, and in our own case
we always identify with a given region of maximal invariance.
The phenomenal unit of identification (UI) can change dynamically, whenever the system discovers a new region of maximal
invariance.
Let us look at some informative examples. A standard phenomenal property serving as the “target” of this hypothetical and
as-yet unknown mechanism would be the integrated contents of
our current body image, another typical example is the subjective quality of “agency” in the control of bodily actions. Often
both target properties coincide and simultaneously function as
the locus of identification. This is why, in standard situations,
we experience ourselves as embodied agents. Prima facie one
might think that the phenomenal self simply is wherever there
is an experience of causal control, for example in bodily agency.
identification,” namely the representation of an epistemic agent, the currently
knowing self. It is also interesting to note how OBEs, phenomenologically, are
not states of full disembodiment. On the contrary, there always seems to be
a spatially located phenomenal self, even if its embodiment is reduced to a
purely spatial point of epistemic agency. Perhaps, it would therefore be better
to speak of mislocation or “misembodiment”
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Why are dreams interesting for philosophers?
However, the data about asomatic OBEs and bodiless dreams
show a more differentiated picture. First, explicit body representation is not necessary, because an extensionless point in space
is sufficient for phenomenal self-identification. Second, bodily
agency is not a necessary condition either, because during these
episodes the experience of mental self-control and epistemic
agency suffices for creating a 1PP. Third, as the sense of selfhood
seems to remain robust even in those asomatic OBEs and bodiless dreams in which there is neither an experience of motion in
space nor goal-directed mental activity, it is plausible to assume
that agency is not a constitutive element for the minimal unit of
identification.
But what other candidates for the UI are there? A more specific example would be the geometrical origin of the visuospatial
1PP, as an extensionless point in space (Blanke and Metzinger,
2009). And the most general target property for the mechanism
generating the distinct experience of “I am this!” is the unity
of consciousness as such. This is, of course, a fact already well
known from the phenomenology of meditation and prolonged
spiritual practice.8 Long-term meditators describe states of consciousness in which they identify with the non-personal quality
of conscious awareness as such. However, it is interesting to note
how the “pure consciousness” variant of self-identification can
also be found in OBEs and dreams (see section Bodiless Dreams
below).
The existing empirical material seems to be ambiguous
between asomatic OBEs in terms of the only locus of identification being the arguably minimal unit of an extensionless point in
space, and aparasomatic OBEs in terms of the “pure consciousness” variant (i.e., the unit of identification being phenomenality
per se, or the global unity of consciousness as such, as frequently
described when referring to mystical or meditation experiences,
see Fasching, 2008; Hölzel et al., 2011). This is partly a conceptual
issue, because it is not clear whether pure, minimal self-location
in terms of identifying with an extensionless point in space counts
as the minimal form of being embodied or not. It is also unclear
exactly which type of experience subjects had in mind when
they were asked about “bodiless” experiences.9 For the 18.8% of
8 For an introduction and references see Fasching (2008).
9A
further important conceptual issue is the possibility of phenomenal indeterminacy. This means that in some cases there may not even have been a
“phenomenological fact of the matter” concerning the object of identification. In her 1982 monograph, Susan Blackmore discusses findings of Green,
Poynton, Rogo and the Society for Psychical Research and points out an interesting possibility: “This indicates that for many OBEers the question of
whether or not there is another body is so uninteresting that they say nothing about it, even in accounts several pages long. Perhaps this is part of the
reason for varied results. Even if you force people to answer the question
they may not really know whether they had another body or not.” (cf. p. 66)
This supports what Windt (2014, chapter 7) says about the phenomenal indeterminacy of bodily experience, namely that phenomenal disembodiment is
probably rare, but that phenomenal indeterminacy in dreams might be quite
widespread, though typically unreported. However, unlike Blackmore, Windt
defends the additional claim that this is not just a factor of not knowing
whether or not one had a body, but of there being no fact of the matter in
experience itself. Interestingly, this is also the most complete way of lacking a
body, because these are not even cases of feeling the absence of the body as in
“pure self-location”, but of the body dropping out of experience altogether.
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subjects describing their OBEs as “bodiless” in the Wolfradt study
cited above, it is not clear that some of them did not actually
belong to the subset of those 21.9% who found themselves “in
a cloud, fog, or at a point in space” (emphasis TM). For the classic
review of Alvarado cited above, it is not entirely clear how many of
the 31% of “pure consciousness”-subjects were perhaps also experiencing themselves as visuospatial “points in space” (a subset of
the 28%), because it is not exactly clear what subjects (and investigators) actually understood or meant in the questionnaire. It is
plausible to assume that an egocentric model of perceptual space
was still in existence in both types of phenomenal configuration—
but exactly what was the unit of identification? In aparasomatic
OBEs it might well have been the maximal unit of “pure” consciousness as such. Many of those subjects having experienced
an identification with an extensionless point in space may actually misdescribe their experience as “pure consciousness”, while
still having had a weak 1PP (as defined in Blanke and Metzinger,
2009).
Here is the philosophical puzzle: What, conceptually, should
be the semantic cut-off point between genuine bodily self consciousness and the minimal experience of mere conscious
self-location at an extensionless point in space? In analytical
geometry, a point is a null-dimensional element of a specific vector space, all other geometric objects can be described as sets of
points. On the level of mental representation, a point in space
clearly is a form of spatial mental content10 . Therefore, our theoretical framework could perhaps be made more parsimonious,
namely by conceptually reducing minimal self-consciousness to
spatiotemporal self-location. But what, phenomenologically, is
the difference between “I am this, here and now!” and “This,
here and now!”? This is where dream research becomes important for philosophers of mind: Philosophers of mind can greatly
profit from the data and fine-grained phenomenological constraints produced by empirical research programs on dream
consciousness, and dream researchers should listen to philosophers in refining their own questionnaires and experimental
designs.
Bodiless dreams
A rare, but well-known phenomenon are dreams in which there
is only an abstract self-representation in terms of a model of the
dreamer as an epistemic subject, identified with an extensionless point in perceptual space. What exactly does this mean? In a
first-order approximation, there seem to be three central defining
characteristics:
• Minimized spatial content (body perception is reduced to a
point in space);
• Phenomenal epistemicity (the stable experience of being a
knowing entity);
• Self-identification.
10 For the purposes of this paper I will ignore the problem of temporal selflocation and the issue of mental self-location in a temporal frame of reference.
Clearly, there is a minimal form of temporal content as well, and it is an important source of invariance. See (Metzinger, 2003a), sections 3.2.2 and 6.2.2, and
(Metzinger, under review).
Frontiers in Psychology | Consciousness Research
Why are dreams interesting for philosophers?
“Abstract self-representation” means that the currently conscious
self-model does not contain any perceptual or spatially extended
features of bodily content: There is no visual, auditory, olfactory, gustatory, tactile, proprioceptive, vestibular, nociceptive,
thermal, or interoceptive information represented on the level
of bodily self-consciousness (for an example, see Cicogna and
Bosinelli, 2001, p. 32, Ex. 11). Spatial embodiment is minimal,
because it is confined to an extensionless point in space (Box 2).
“Epistemicity” means that the dreamer is modeled as a knowing
self, as an entity that has knowledge about the world, but also
actively expands this knowledge, for example through controlling
the focus of attention or by remembering, forming new concepts,
active inference, and so on. Most bodiless dreams occur during
lucid dreams, and it only is here where the knowing self is truly
stable over time. “Phenomenal epistemicity,” as the second defining characteristic, simply means that on the level of conscious
experience, the dream self is represented as something that stands
in an epistemic relation to the world, in the relation of knowing,
thinking, actively guiding attention, of just trying to understand
what is going on. Therefore, let us call this type of conscious
self-representation an “epistemic agent model” (EAM)11 . In bodiless dreams, this abstract EAM is the unit of identification. It
generates the phenomenology of “I am this abstract, knowing
self!” Of course, there can be multiple EAMs in social dreams—
other dream characters representing other knowing selves—but
only one of them serves as the locus of identification. Please
also note that the presence of an EAM as the unit of identification does not imply that any form of knowledge, in a more
rigorous epistemological sense, is actually in existence: All we
have is the phenomenology of knowing. The third major defining
characteristic is self-identification, namely, at or with an extensionless point in perceptual space and with the EAM. Bodiless
dreams are still perceptual spaces, they have an egocentric geometrical structure including a point of origin and a perspective,
and therefore, they automatically include a weak 1PP in the
sense of Blanke and Metzinger (2009). However, self-location is
also maximally abstract: It only includes a point in space and
a point in time, a Here and a Now. Let us look at one simple
example:
I was thinking of problems about my examination . . . I had
the image of the open book . . . nothing else. (Occhionero and
Cicogna, 2011, p. 1013; see also Occhionero et al., 2005, p. 79,
Example 2)
11 We
can now characterize lucid dreams as those in which the brain has
already succeeded in establishing a stable EAM, whereas non-lucid dreams
appear more as an ongoing, and sometimes desperate, attempt to consolidate enduring epistemic relationships to the dream world, of gaining control
over attention and one’s own cognitive processing, the same point applies
for mind wandering, see Metzinger (under review). The non-lucid dreamer
experiences epistemic agency mostly as a search for stability, or an ongoing,
constantly perturbed attempt to understand the situation, whereas the lucid
dreamer is capable of goal-directed mental behavior, in thinking, remembering, and focusing attention on specific target objects. A helpful and more
detailed discussion of “cogitative” and “doxastic” indeterminacy as characterizing cases where phenomenal epistemicity is lost can be found in (Windt,
2014) (Chapters 9 and 10).
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First, we have a rudimentary perceptual space, containing
only one object (the book) and one sensory modality (vision).
Interestingly, it is not clear if it is phenomenologically adequate
to speak of full immersion or a complete “situation model”
here (because the “image of the book” might have been floating
in space by itself), but there is a visual observer in an egocentric frame of reference—if there weren’t, the experience of
seeing of the book would have been described in a very different manner. Second, there is an EAM: There is a cognitive
subject, a thinker of thoughts about the upcoming examination,
and we can plausibly assume that an attentional agent, a subject
of attentionally controlled visual content was also given in the
experience.
The most relevant point is that in bodiless dreams the abstract
unit of identification and the unit of self-location coincide: The
EAM is represented as identical with the origin of the weak 1PP.
Therefore, it may be possible to integrate conditions 1 and 2
stated in our original definition of MPS, because recent research
has demonstrated the high prevalence of asomatic OBEs and
bodiless dreams in which the sense of selfhood remains stable. Conceptually, the self-identification condition would then be
reduced to the self-location condition, and we would have arrived
at a more parsimonious definition of minimal self-consciousness.
As Jennifer Windt (2010, p. 312) has pointed out, a better and
refined definition of MPS could then be as “transparent selflocation in a spatiotemporal frame of reference.” This generates
two interesting new questions for research, one conceptual, one
empirical:
• Is the “epistemicity” of the EAM a necessary condition for
the occurrence of a robust form of phenomenal selfhood? In
other words, is every conscious self necessarily a (phenomenologically) knowing self, or should we treat the conjunction
of “transparency” and “self-location” in itself as a sufficient
condition?
• Can dream research demonstrate the occurrence of dreams
in which the second element of Windt’s definition is given,
but in which the transparency constraint is not satisfied? In
other words, are there fully lucid, phenomenally opaque, and
bodiless dreams for which it is true that spatiotemporal selflocation is itself experienced as a form of (mis)representational
content?
In developing her own definition of dreams as “immersive spatiotemporal hallucinations” (ISTH) Jennifer Windt writes:
I suggest that the crucial factor that distinguishes dreaming from
non-dreaming sleep experiences is precisely the sense of spatial
and temporal presence in the dream. In a very basic sense, there
is a hallucinatory scene that is organized around an internal, spatiotemporal first-person perspective (1PP) as well as a sense of
spatiotemporal self-location, i.e., the sense of occupying a space
(even a point will be extended in a minimal sense), plus an experienced “now” and the experience of duration. While Blanke and
Metzinger (2009) use the term weak 1PP to refer to a visuospatial
or auditory 1PP, I use it here in the more reduced sense of a purely
spatiotemporal 1PP. On this level, I think the distinction between
a spatiotemporal 1PP and a sense of spatiotemporal self-location
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Why are dreams interesting for philosophers?
disappears: both refer to the phenomenological property of being
located at (and relative to) a certain point in space at a certain
point in time. (2010, p. 304)
And she goes on to explain:
Finally, if this analysis of dreams as ISTH is correct, it shows that a
minimal form of self-experience or minimal phenomenal selfhood
(MPS) does not require what Blanke and Metzinger (2009: 12)
call “a passive, multisensory and globalized experience of ‘owning’
a body.” They suggest that this sense of “‘global ownership’—
functionally defined as availability of an integrated, transparent,
and global representation of the spatiotemporally situated body—
is the simplest form of self-consciousness.” While I agree with
their conclusion that MPS “is constituted by something ‘less’
than agency” (Blanke and Metzinger, 2009: 12), I would submit
that the subjective sense of presence—or at least the retrospective
description of an experience as having involved the presence of
a self—involves something even less: the sense of immersion or of
(unstable) location in a spatiotemporal frame of reference. Neither
global ownership nor a visual 1PP, however, are necessary for MPS.
For this reason, the ISTH model of dreaming is also directly relevant for the philosophical understanding of self-consciousness.
(ibid., p. 306).
Now we can state more clearly why dream research is relevant
for philosophers: It is one of the best currently available scientific
strategies for grounding the 1PP (see Barsalou, 2008; Metzinger,
2014 for the relationship between “grounded cognition” research
programs and subjectivity). It is also the best global contrast condition for isolating MPS. There are only two other sources for
investigating MPS and bodiless subjectivity, i.e., states in which
body representation is absolutely minimal, but in which a stable
sense of selfhood and an “asomatic 1PP” can be found: The scientific observation of OBEs and meditation research. However,
both asomatic OBEs and “pure consciousness” experiences in
meditators are rare phenomena. The prevalence of spontaneously
occurring and asomatic OBEs in healthy subjects is simply too low
to make them amenable for investigation under controlled conditions in sleep labs (see Irwin, 1985; Blackmore, 1982/1992 for
substantial overviews). The second wave of rigorous meditation
research has only begun (see Lutz et al., 2007; Chiesa and Serretti,
2010; Hölzel et al., 2011 for review), but it seems clear that states
of consciousness in which subjects identify with the non-personal
quality of conscious awareness as such only occur in few longterm meditators or trained monks, and often unpredictably. In
addition, autophenomenological reports from OBEers and longterm adherents to a specific form of spiritual practice may also
be characterized by stronger ideological biases and distortions
through individual belief systems than dreams. There is considerable promise in virtual reality (VR) as new tool for research (see
Sanchez-Vives and Slater, 2005; Slater et al., 2010) in this area,
but as yet all such novel experimental strategies are heavily constrained by the fact that they take waking consciousness and its
interoceptively and perceptually rich self-model as an inevitable
starting point (Seth, 2013). Dreaming occurs spontaneously in
7 billion people on the planet, and multiple times every night.
Thousands of dream reports gathered by scientific researchers are
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already in existence, and they could be statistically re-evaluated.
Bodiless dreams are probably rare, but as dreams are generally
more frequent and easier to evaluate, there is still a better chance
of finding such reports than for OBEs. Although many (but not
all) reports of “asomatic dreaming” seem to come from lucid
dreams (LaBerge and DeGracia, 2000), thereby making the target
phenomenon potentially more controllable, there is also an inherent risk of specific biases in this subset. Most importantly, the
questions asked by dream researchers should be refined, for example in accordance with our discussion above, resolving conceptual
ambiguities inherent in existing studies. Here is a non-exhaustive
list of desiderata for future research:
• What is the minimal unit of identification in the dream state?
• What is the maximal unit of identification in the dream state?
• Are there “minimax” states, in which a subject, for example,
feels identical with an extensionless point in space and the unity
of consciousness at the same time?
• Are there opaque types of spatiotemporal self-location
(i.e., without the accompanying phenomenology of selfidentification), for example during “aparasomatic” lucid
dreams? What is their prevalence?
• In the absence of an EAM, is there any empirical evidence for
other forms of conscious self-representation in the dream state?
PART 2
PHILOSOPHY AND DREAM RESEARCH: PROMISING
CONTACT POINTS
The central claim of this paper is that empirical research on
dreaming is highly relevant for philosophy of mind and cognitive science, as well as for the flourishing interdisciplinary
field of consciousness research in general. It shatters theoretical intuitions, offers a wide range of important bottom-up
constraints for a comprehensive theory of mind, and thus is
a constant provocation for old-school analytical epistemology
and armchair philosophy of mind. But modern philosophy has
a lot to offer to dream researchers as well: More precise phenomenological descriptions, thorough conceptual clarification,
and methodological criticism. Let us look at four short examples
where interdisciplinary cooperation could be most innovative and
promising.
EXAMPLE 1: THE CONCEPT OF A “FIRST-PERSON PERSPECTIVE”
For philosophers, the concept of a “first-person perspective” is
highly relevant, and for a wide range of reasons. For example,
one classical philosophical issue is the question of what exactly it
means that conscious mental states are “subjective” states. What
exactly does it mean that conscious experience is often bound
to an individual 1PP? We lack an empirically grounded theory
of subjectivity, a model of the 1PP as a naturally evolved phenomenon. Here, my point is that having a 1PP is not a unitary,
but a graded phenomenon, and that dream research can make
decisive contributions in functionally dissociating different levels
of this specific research target.
An important conceptual distinction is between two ways of
being directed at the world as a knowing self, one, by attention, and two, by cognition, that is, either by a subsymbolic,
Frontiers in Psychology | Consciousness Research
Why are dreams interesting for philosophers?
non-linguistic process of selective precision optimization and
resource allocation (i.e., on the level of perception) or by being
a subject that is directed at the world by forming new concepts
about it. There clearly is a phenomenological difference between
being an attending self and being a thinking self. And on a functional level it is, for example, plausible to assume that there are
many animals on this planet that can selectively control their
attention, but are unable to form concepts. A stronger contrast
exists between human non-lucid dreams and human standard
wake states, where in the dream state both types of 1PP are either
absent or extremely unstable and short-lived, as opposed to the
more robust and temporally extended subjective perspective of
waking life. In particular, the transition toward a richer and more
stable 1PP can be precisely observed in the different stages of
prelucidity and lucidity. Because this contrast is stronger during
dreams than in wakefulness, the non-unitary and graded nature
of the 1PP can be investigated in a much clearer way in dreams
than in waking consciousness.
Above, I introduced the concept of an “epistemic agent model”
(EAM), as a specific type of conscious self-representation. This
means that on the level of conscious experience, the self is represented as something that stands in an epistemic relation to
the world, in the relation of knowing, thinking, actively guiding
attention, of just trying to understand what is going on. Dream
research could allow us to differentiate the functional and representational layers that constitute an EAM. To see the contact
points between philosophy and dream research more clearly, let
us look at the very specific connection between subjectivity and
attention in the dream state.
Attentional agency (AA; see Metzinger, 2003a: 6.4.3., 2006;
Box 1) is a phenomenal property, as is the case for pain or the
subjective quality of blue in a visual color experience. AA is the
conscious experience of initiating a shift of attention, of controlling and fixing its focus on a certain aspect of reality. We
know that this property is selectively missing during non-lucid
dreaming, but likely also during infancy, dementia, or severe
intoxication syndromes. AA involves a sense of effort, and it is the
phenomenal signature of the functional ability to actively influence what you will know, and what, for now, you will ignore.
AA is fully transparent: The content of your conscious experience is not one of self-representation or of an ongoing process of
self-modeling, of depicting yourself as a causal agent in certain
shifts of “zoom factor,” “resolving power,” or “resource allocation,” and so on, but simply of yourself selecting a new object for
attention.
Under a predictive coding approach (Friston, 2010), having
an attentional 1PP can be fruitfully associated with secondorder statistics or precision optimization (Hohwy, 2013) and with
the internal modeling of mental resource allocation (Metzinger,
2003a), but on the functional level of global availability (i.e.,
consciously) and on the representational level of subsymbolic
dynamics (i.e., non-conceptually). The attentional 1PP is conscious, but non-conceptual. What we call “attention” when using
folk-psychological, everyday concepts, and when describing the
mind from a third-person perspective, is a process by which the
brain allocates computational resources to regions in which a
deeper, more detailed form of processing is needed. In some cases,
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this is a saliency-driven, bottom-up process, in other cases involving “top-down attention,” it involves a kind of inner agency, an
active process of selecting certain perceptual or cognitive contents
for closer inspection and deeper processing. It is important to
note, however, that it is one thing for a system to have the capacity for selective, top-down attentional control, and another for
the same system to also know that it possesses this capacity. One
centrally relevant theoretical idea is that the conscious experience
of directing one’s attention involves creating an internal model
of an ongoing process of resource allocation, thereby establishing a self-representational kind of knowledge for the organism.
The essence of this knowledge is that the organism is not only
a bodily, but also an epistemic agent—a being that is currently
attempting to expand its knowledge by actively directing its own
capacities for information processing at the world and at its own
states.
If this is correct, then it is clear why dream research is centrally
relevant for the project of understanding how a “knowing self,”
a subject of experience emerges. Dream researchers and empirically informed philosophers have collaborated to investigate those
changes in the human self-model that are necessary in causally
enabling the transition from non-lucid to lucid dreaming, have
recently made progress in conceptually differentiating stages of
lucidity as well as in isolating the neural correlates of this specific target property (Windt and Metzinger, 2007; Voss et al.,
2009; Noreika et al., 2010; Dresler et al., 2012; Voss et al., 2013).
Obviously, this kind of research possesses great relevance for the
philosophy of mind, because it gives us a much deeper understanding of what we mean by concepts like “subjectivity” or
“epistemic agency.”
Here is one example how dream researchers could make a
contribution to the project of grounding the 1PP. The spatial
correlation between eye-movements in the dream body and the
physical body has served as the foundation for a number of ingenious studies homing in on the neural correlate of “lucidity” (i.e.,
the rare occurrence of realizing that one is dreaming during the
dream state itself; see LaBerge et al., 1981; Voss et al., 2009, 2013;
Dresler et al., 2012; for discussion see Metzinger, 2003a; Windt
and Metzinger, 2007; Windt, 2014). In these experiments, lucid
dreamers actively send signals to the experimenter via deliberate
eye movements, which can be read off the EOG and are retrospectively confirmed by the dreamers themselves. This discovery
is theoretically important, because it gives us a first candidate for
a grounding relation connecting the conscious dream body with
low-level physical dynamics (measurable neural activity controlling eye movements), perhaps linked through an unconscious
body-model mediating the active exploration of visual space
(Dement and Kleitman, 1957; Leclair-Visonneau et al., 2010).
Phenomenal self-consciousness and self-related cognition can be
grounded in different ways, including neurally realized simulations, bodily processes, and situated action (Barsalou, 2008:
619). Interestingly, here we find all three of them: Gaze control
in the lucid dream state clearly is a form of virtually situated
action, because it involves motor control plus attentional resource
allocation in a virtual environment; it uses an internal simulation of the body-as-visually-attending (the self-model of the
dream state, see Windt and Metzinger, 2007; Windt, 2014 for
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Why are dreams interesting for philosophers?
details); and it has dynamic, structure-preserving bodily correlates. The successful control of gaze direction in the lucid dream
state is what anchors selective, high-level visual attention (including the conscious sense of “attentional agency”) in low-level,
non-representational features of bodily movement. Here we have
an example of a specific and functionally persistent grounding
relation connecting the origin of the 1PP to unconscious processes, and in a situation where bodily action is almost entirely
absent. It would be a valuable contribution to describe the necessary and sufficient conditions for this grounding relation to
be realized in the dream state in a more precise way, and especially the temporal dynamics, the different stages though which
it appears and disappears in the dream state. One might also
interestingly connect this to the issue of describing the “minimal
unit of identification” discussed in Part 1: Are there any relevant differences in bodiless dreams or asomatic OBEs? Perhaps
bodiless dreams are the class of phenomenal states in which the
relationship between MPS and the emergence of an EAM can be
studied best.
EXAMPLE 2: COGNITIVE PHENOMENOLOGY, MIND WANDERING, AND
MENTAL AUTONOMY
“Cognitive phenomenology” is a label for a new subfield of
research in philosophy of mind that focuses on the phenomenal
character of occurrent non-sensory mental states like thoughts
or wishes, on the distinct subjective quality that goes along with
thinking (see Bayne and Montague, 2011 for a good overview).
Some philosophers claim that there is a proprietary, distinctive and
individuative phenomenology of higher cognitive processing that
cannot be derived from sensory phenomenology, others deny this
claim. Very obviously, research on the phenomenology of mentation in REM- and NREM-sleep, or on the characteristics of the
thought process during lucid vs. non-lucid dreaming is directly
relevant here (Box 2).
“Mind wandering” names a new field of research in psychology that has important, but unexplored connections to dream
research and implications for cognitive phenomenology as well
(Schooler et al., 2011; Metzinger, under review). Mind wandering
takes place during perceptual decoupling, when spontaneously
occurring mental events disengage attention from perception,
leading to stimulus-independent trains of thoughts, for example
during episodes of “daydreaming” or “zoning out” while reading
(Smallwood and Schooler, 2006). In the absence of demanding external tasks, during routine activities or while resting we
often lose the quality of attentional agency as defined above.
Attentional focus is “hijacked” by representational processes not
focused on the here and now any more, and importantly, we
are often unaware of this very fact for extended periods of time.
Mind wandering takes place during 30–50% of our waking life
(Kane et al., 2007; Killingsworth and Gilbert, 2010; Schooler et al.,
2011). Empirical findings show that we have the ability to take
explicit note of ourselves as engaging in mind wandering, but only
intermittently and only rarely. While mind wandering clearly is
a recurring, marked loss of cognitive control and interferes with
online sensory processing (for an excellent, concise overview of
performance costs, see Mooneyham and Schooler, 2013, p. 12,
Table 1) it may also possess an important functionality for
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creativity (Baird et al., 2012), attentional cycling in multiplegoal configurations, dishabituation, or autobiographical planning
(Baird et al., 2011; Mooneyham and Schooler, 2013; Stawarczyk
et al., 2013).
Conceptually, mind wandering and dreaming are both interesting to philosophers, because they involve a cyclically recurring decrease in mental autonomy that is not self-initiated and
frequently unnoticed. Autonomy is the capacity for rational
self-control, whereas the term “mental autonomy” (or “Mautonomy”; see Metzinger, under review; Box 2) refers to the
specific ability to control one’s own mental functions, like attention, episodic memory, planning, concept formation, rational
deliberation, or decision making. NREM-sleep mentation and
non-lucid dreaming clearly are also periods during which the
functional property of M-autonomy is absent, although complex cognitive processes are taking place across all sleep stages
(Nielsen, 2000; Fosse et al., 2001; Fox et al., 2013; Klinger, 2013;
Wamsley, 2013; Windt, 2014) and can be sampled, for example using a serial awakening paradigm (Noreika et al., 2009;
Siclari et al., 2013). Here, my thesis is that the recurring loss
of mental autonomy is one major characteristic of our cognitive phenomenology, and that both research on dreaming and
mind wandering have developed important research tools to
investigate this hitherto neglected aspect further (like external
probing, or systematic questions after sleep laboratory awakenings; see also Smallwood, 2013). It is empirically plausible
to assume that a considerable part of our own cognitive phenomenology simply results from a frequent failure of executive
control (McVay and Kane, 2009). I would claim that this actually
is one of the most important functional and phenomenological characteristics of human self-consciousness, as a matter of
fact, one of its most general, principal features: The almost
constant presence of subpersonal and automatically generated
mental activity (as generated by the default-mode brain network; Raichle et al., 2001; Buckner et al., 2008), in combination
with a frequent inability of the executive-control system to shield
primary-task performance off against interference from these
subpersonal thought processes. If I am right, autonomous cognitive self-control is an exception, and not the rule (Metzinger,
under review).
There are many other important connections between dreaming and waking mind wandering. First, the occurrence of dream
lucidity and what researchers in mind wandering call “metaawareness” (i.e., the “explicit knowledge of the current contents
of thought,” see Schooler et al., 2011, p. 321) share many features, such as restoring mental autonomy. On the other hand,
lucid lapses and mind-wandering lapses can both plausibly be
interpreted as the disintegration of the EAM: The subject of experience loses the quality of epistemic agency. Second, dreaming
and mind wandering may both share positive functionalities, such
as the encoding of long-term memory (Christoff et al., 2011:
263p.), complex, preparatory motor planning and prospective
autobiographical planning, or creative incubation. For example,
Mooneyham and Schooler (2013: 15) hypothesize that “mind
wandering may play a role in successful incubation (i.e., in coming up with novel solutions to previously presented problems
when presented with them after the incubation period).” Third,
Frontiers in Psychology | Consciousness Research
Why are dreams interesting for philosophers?
there is considerable overlap between the neural correlates of
mind wandering (Gruberger et al., 2011; Christoff, 2012) and
those of the dream state (Solms, 2011), giving new support to
the classical idea that there may be an uninterrupted continuum between controlled personal-level thought in wake states,
mind wandering, and dreaming as an “intensified” version of
mind wandering (Fox et al., 2013, figure 3; Wamsley, 2013).
Fourth, in dream research there is the theoretical problem of
“false lucidity”: There are reasons to believe that some subjects reporting lucid dreams were actually awake and successfully controlling the plot of their waking fantasies. In addition,
there are different concepts of “lucidity” in academic research
(Noreika et al., 2010; Voss et al., 2013), but do all subjects
possess mastery of the concept of “lucidity”? If yes, what is
their concept of lucidity? In mind wandering, the experience
of oneself having actively regained meta-awareness (and thereby
mental autonomy) could be an illusion of control over a mental event, which was really triggered by an unconscious process
(Wegner, 2002; Schooler et al., 2011, Box 1). Although mostly
neglected by philosophers12 , both theoretical issues are directly
relevant to the project of cognitive phenomenology. In particular, the specific “phenomenology of insight” going along with
becoming lucid in a dream or with successfully catching oneself mind-wandering may prove to be of central importance:
Is this phenomenology an epiphenomenal, post-hoc confabulation on the level of our conscious self-model, or does it possess
a genuine epistemic status and a distinct causal role in mental
self-regulation?
EXAMPLE 3: EMBODIMENT
For a quarter century now, the notion of “embodiment” has been
central in philosophical discussions of the relationship between
intelligence and its physical basis (see Robbins and Aydede, 2009;
Shapiro, 2012, 2014). How do properties of the body constrain
our model of the world? Does the body itself play a constitutive role in cognitive processing? What is the role of unconscious
and conscious body representations for higher forms of intelligence and for the phenomenology of bodily self-consciousness?
To give an example, in earlier publications, I have claimed that
the dream state, which is accompanied by sleep paralysis, often
is an example of explicit body-representation (we experience a
dream body), but in the absence of active low-level embodiment, simply because the physical body is inert and fully paralyzed13 . Dreamers, therefore, are not fully embodied agents (e.g.,
Metzinger, 2003a: 256, Metzinger, 2009). The “functional disembodiment hypothesis” (Windt, 2014) says that the dream state
is characterized by a functional disconnection from the sleeping body such that real-body inputs do not enter into the dream
12 Notable exceptions are Jean-Paul Sartre (1940), Colin McGinn (2005, 2009)
or Jonathan Ichikawa (2008; 2009; for a critical philosophical evaluation, see
(Windt, 2014), chapter 6). Sartre, McGinn, and Ichikawa all assume that we
control our daydreams, and try to show that the same is true for nocturnal
dreams – but based on empirical evidence from research on mind wandering
(see section 4.2), this claim is even empirically implausible with respect to
daydreaming itself.
13 This section draws on a discussion also presented in (Metzinger, 2014).
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Why are dreams interesting for philosophers?
Box 1 | Levels of self-consciousness
1. MPS (minimal phenomenal selfhood; Blanke and Metzinger, 2009)
Paradigmatic autophenomenological report: <I am this, here and now.>
Self-identification as transparent spatiotemporal self-location:
a. A conscious self-representation that is not experienced as a representation.
b. Satisfaction of transparency-constraint leads to the phenomenology of identification.
c. Data from bodiless dreams and asomatic out-of-body experiences show that pure spatiotemporal self-location suffices for a robust
sense of self (sections Asomatic OBEs and Bodiless dreams).
d. MPS can be experimentally controlled (e.g., De Ridder et al., 2007; Ehrsson, 2007; Lenggenhager et al., 2007)
e. Self-location in an egocentric frame of reference creates a weak, purely geometrical first-person perspective (1PP; see below), which
is a necessary constituent of MPS.
f. Once MPS has been established, it can function as the origin of richer and more complex forms of 1PP
2. BA (bodily agency)
Paradigmatic autophenomenological report: <I am an embodied agent.>
Self-identification with an extended body image, plus causal self-control.
a. A spatially extended, conscious body-representation that is not experienced as a representation.
b. A holistic representation of the system as an entity that acts physically, for example by changing its position in space; and/or
c. has the potential for physical agency.
3. AA (attentional agency)
Paradigmatic autophenomenological report: <I am a self in the act of controlling its attentional focus.>
Typically, self-identification with an extended body image, plus attentional self-control.
a. A conscious self-representation as an entity currently controlling mental resource allocation; and/or
b. having the potential for controlling subsymbolic mental resource allocation.
c. Data from bodiless dreams and asomatic out-of-body experiences show that pure spatiotemporal self-location can coexist with AA
(sections Asomatic OBEs and Bodiless Dreams).
4. CA (cognitive agency)
Paradigmatic autophenomenological report: <I am a thinking self.>
Typically, self-identification with an extended body image, plus high-level cognitive self-control.
a. A conscious self-representation as an entity currently controlling high-level cognitive processing, including quasi-symbolic,
conceptual, and propositional contents; and/or
b. having the potential for controlling high-level cognitive processing, including quasi-symbolic, conceptual, and propositional content.
c. Data from bodiless dreams and asomatic out-of-body experiences show that pure spatiotemporal self-location can coexist with CA
(sections Asomatic OBEs and Bodiless Dreams).
5. EAM (epistemic agent model; see section on Bodiless Dreams)
Paradigmatic autophenomenological report: <I am a knowing self>
Conscious self-representation of the system as an individual entity capable of epistemic self-control:
a. as currently standing in and/or actively constructing knowledge relations to certain parts of the world; and/or
b. as having the ability to actively establish such relations.
c. AA is sufficient for having an EAM, CA is not a necessary condition.
6. 1PP (first-person perspective; Metzinger, 2003a,b, 2006, 2007; Blanke and Metzinger, 2009)
Paradigmatic autophenomenological report: <I am directed at the world>
Conscious representation of the system as currently being directed at the world, either by bodily or by epistemic agency. Comes in
many variations, paradigmatic examples are:
a. Being directed at a physical goal-state via ongoing bodily agency (BA).
b. Being directed at a perceptual object via high-level attentional control (AA).
c. Being directed at abstract cognitive content (e.g., concepts or propositions) via cognitive self-control, quasi-symbolic thought, etc.
(CA).
and internally experienced dream movements are not enacted
by the sleeping body. On this view, the phenomenal body is
completely independent of the physical body. I also pointed
out a single, highly interesting exception, namely the reliable
directional correspondence between dream-eye movements and
real-eye movements: There is at least one sense in which the
phenomenal dream self is not completely disembodied in the
functional sense (Metzinger, 2003a, p. 261; see the discussion of
AA above).
www.frontiersin.org
The generalized version of the functional disembodiment
claim, however, has now been refuted, as it can be shown
that more than one minimal form of functional embodiment
is preserved during REM-sleep dreams (cf. Windt, 2014,
chapter 8). Real-body stimulation (e.g., sprays of water on the
skin, Dement and Wolpert, 1958; electric stimulation, Koulack,
1969; blood-pressure-cuff stimulation on the leg, Nielsen, 1993;
Sauvageau et al., 1993, 1998; Nielsen et al., 1995; vestibular stimulation, Hoff, 1929; Hoff and Plötzl, 1937; Leslie and
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Why are dreams interesting for philosophers?
Box 2 | Glossary of Terms.
OBE
An “out-of-body experience,” in which the experiential subject has the feeling of being located outside of its physical body as
represented, often in combination with a perceptually impossible external perspective. Asomatic OBEs are characterized by MPS, an
EAM, plus a weak spatial 1PP (see Box 1; Metzinger, 2003a, 2009).
Asomatic OBE
An out-of-body experience in which the experiential subject lacks any spatial form, because it is phenomenologically identified with an
extensionless point in space, external to the physical body as represented. Asomatic OBEs are characterized by MPS, an EAM, plus a
weak spatial 1PP (see Box 1).
Dream
A complex hallucinatory experience occurring in sleep or during sleep-wake transitions, in which the experiential subject is fully
immersed and localized in a spatiotemporal scene. Dreams are characterized by severe, and frequently unnoticed deficits in memory,
cognition, and rationality. AA and CA are mostly absent, the EAM is highly unstable (see Box 1; Windt, 2010, 2014).
Bodiless Dream
A dream in which conscious body representation is reduced to an extensionless point in space, and there is self-identification plus,
typically, a knowing self. Most bodiless dreams seem to be lucid dreams, and as such they are characterized by MPS, an EAM, plus a
weak spatial 1PP (see Box 1). In non-lucid bodiless dreams, the EAM is absent or unstable.
Lucidity
The rare phenomenon that a dreamer is aware of the fact that he or she is currently dreaming. Lucidity can be conceptually analyzed
as the gradual stabilization of an EAM. There are different types and stages of lucidity (Windt and Metzinger, 2007; Noreika et al., 2010),
and there has been recent progress in isolating the neural correlates of such transitions (Voss et al., 2009, 2013; Dresler et al., 2012). The
“meta-awareness” that is regained in dream lucidity may be interestingly related to the termination of mind-wandering episodes during
waking periods (Schooler et al., 2011; Metzinger, under review).
Mind Wandering
Episodes of phenomenologically spontaneous, stimulus- and/or task-unrelated thought (daydreaming, autobiographical planning,
waking fantasies, depressive rumination, etc.). Conceptually, mind wandering can be described as the absence of CA and AA, and as a
transient loss of mental autonomy (M-autonomy; see Metzinger, under review). It is empirically plausible to assume that large parts of
the neural correlate of mind wandering overlap with activity in the default mode network (DMN; Buckner et al., 2008; Christoff, 2012;
Christoff et al., 2009; Stawarczyk et al., 2011).
M-Autonomy
The term “M-autonomy” (for “mental autonomy” as opposed to autonomy in bodily or social action) refers to the specific ability
to control one’s own mental functions, like attention, episodic memory, planning, concept formation, rational deliberation, or decision
making, etc. This ability can be a form of rational self-control, which is based on reasons, beliefs, and conceptual thought, but it does not
have to be. The central defining characteristic is the “veto component”: Being mentally autonomous means that all currently ongoing
processes can in principle be suspended or terminated. This does not mean that they actually are terminated, it just means that the
ability exists, and that the person has knowledge of this fact. A frequently recurring loss of M-autonomy is one major characteristic of our
cognitive phenomenology, and it interestingly characterizes dreaming as well as waking life, whereas lucidity can be seen as M-autonomy
during the dream state [see (Metzinger, under review) for discussion and references].
Phenomenal Unit of Identification
In most dream and waking states there is a unit of identification (UI), determining the conscious experience of “I am this!” In dreams,
the UI can be highly variable, a fact that potentially lends itself to a new way of categorizing dreams and constructing a novel taxonomy.
Minimal UI
The minimal UI is the simplest phenomenal property available for subjective identification. In asomatic OBEs and bodiless dreams the
UI is transparent spatiotemporal self-location (see Box 1).
Maximal UI
The maximal UI is the most general phenomenal property available for subjective identification. Arguably, this is the experiential quality
of consciousness per se (i.e., phenomenality as such) or the integrated nature of our global conscious model of reality (the “unity of
consciousness”). In some aparasomatic OBEs and during advanced states of meditative practice the experiential subject seems to be
identified with the maximal UI.
Ogilvie, 1996) is frequently incorporated in dreams, and indeed
it has been suggested that many typical dream themes—such
as dreams of flying, falling, or being unable to move or flee
from a pursuer—can be explained in terms of illusory own-body
Frontiers in Psychology | Consciousness Research
perception (Schönhammer, 2004, 2005), and the same may be
true for sleep-paralysis nightmares during sleep onset (Cheyne
et al., 1999; Cheyne, 2003, 2005). An early predecessor of this
view of dreams as weakly functionally embodied states (Windt,
October 2013 | Volume 4 | Article 746 | 12
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2014) is the Leibreiztheorie, promoted by 19th century researchers
and extensively discussed and rejected by Freud (1899/2003,
pp. 38–56). On the output side, there is also ample evidence for dream-enactment behavior in healthy subjects (e.g.,
Nielsen et al., 2009) and patients with RBD (REM-sleep behavior disorder; see Schenck, 2005, 2007; Leclair-Visonneau et al.,
2010), as well as some evidence from lucid dreaming suggesting that dream movements are accompanied by measurable
muscle twitches in the corresponding limbs and changes in
heart and respiration rate (LaBerge et al., 1981, 1983; LaBerge
and Dement, 1982; Fenwick et al., 1984; Schredl and Erlacher,
2008).
Are there any empirical examples of bodily experience or stable
cognitive processing in dreams being created completely offline?
Windt (2014, chapter 8) has investigated the issue and points out
that, at the very least, it would be hard to see how there could
be any empirical evidence for saying that such instances of functionally disembodied self-consciousness exist in dreams: state-of
the-art studies investigating the sensory input blockade (Hobson
et al., 2000), or, as Dang-Vu et al. more aptly call it, the “reduced
sensitivity to external salient stimuli” (Dang-Vu et al., 2007, p.
1000) during REM sleep not only explicitly acknowledge that the
degree of sensory incorporation is weakened rather than completely absent in REM sleep, but also use stimulus incorporation
as an important means of studying the underlying mechanisms
in the first place. This suggests that the most plausible and parsimonious explanation of bodily experience in dreams, as well
as the most effective methods used for its study, will appeal to
its real-bodily basis. But there are important conceptual issues
to which dream researchers can make valuable contributions:
The phenomenology of embodiment is grounded in unconscious
body representation, which in turn “bottoms out” in microdynamical processes best described as non-representational, and
which do not involve anything like explicit computation over
discrete, symbolic states (Metzinger, 2014). But what exactly
does “grounded cognition” (Barsalou, 2008) in the dream state
really mean?
There are a number of relevant contact points between dream
research and the burgeoning field of embodiment in philosophy and cognitive science. The two most important questions may be the following: Can the multiple cognitive deficits
seen in the dream state be better understood if we analyze
them as deficits in embodiment, bringing the whole armory of
new conceptual tools developed in current philosophical discussions of embodiment (Shapiro, 2014), situated cognition
(Robbins and Aydede, 2009), or active externalism (Clark and
Chalmers, 1998; Menary, 2010) to bear on the problems at
hand? Are there deeper systematic and/or functional reasons
beyond the brain alone that lead to the multitude of mental
impairments we see during dreaming? Second, if we aim at a
comprehensive theory for the phenomenology of embodied selfhood, empirical constraints produced by dream research can
be extremely fruitful: How determinate (or indeterminate) is
oneiric body representation really (Windt, 2014)? What is the
minimal unit of identification (see Part 1 above), and how can
dream research inform conceptual work about the necessary and
sufficient conditions for MPS (Blanke and Metzinger, 2009; see
www.frontiersin.org
Why are dreams interesting for philosophers?
section Minimal Phenomenal Selfhood: The Original Hypothesis
above)?
EXAMPLE 4: SELF-DECEPTION, EPISTEMOLOGY AND THE ARGUMENT
FROM COGNITIVE CORRUPTION
Could there be a radical form of philosophical skepticism, much
more radical than the systematic process of doubt in Descartes
methodological skepticism, which claims that even during the
most critical, rational self-reflection it is possible to be fundamentally wrong about the reliability of one’s own cognition? Could
we enjoy the cognitive phenomenology of rationality, insight, or
certainty while being fundamentally wrong about the epistemic
status of our own mental states? Dream research, it seems, delivers
a direct proof of concept. It demonstrates that unnoticed rationality deficits are possible at any point of our conscious lives. Jennifer
Windt is the first author to systematically investigate this particularly promising contact point between philosophy and dream
research, which has mostly been overlooked by professional epistemologists. She writes:
In a dream, one can have the impression of engaging in rational
thought or remembering something about one’s waking life and
be completely wrong. The phenomenology of knowing, thinking, and remembering seems particularly vulnerable to this type
of corruption in the dream state. This type of dream deception,
then, is not so much deception about the nature of the dream
world as deception about the reliability of one’s current cognitive abilities. It is epistemologically troubling because it brings the
threat of deception even closer to home: whereas Cartesian dream
deception has us deceived about the perceptual world and our
bodies, deception from corrupted cognition has us deceived about
our minds. Consequently, we can never be sure of being truly
rational, at any given moment. (Windt, 2014, section 10.2.2)
This point, however, is not only of great relevance to philosophical epistemology and the project of a “cognitive phenomenology” discussed above (in section Example 1: The Concept of
a “First-Person Perspective”). It also bears on the methodology of dream research itself, because it calls into doubt the
status of dream reports. In principle, subjects in sleep laboratories could suffer from massive memory losses or distortions, or
confabulate about their own phenomenology without knowing
(Rosen, 2013). In practice, however, when taking into account
all our background knowledge, prior probabilities and considerations of simplicity, we are justified in a simple inference to the
best explanation stating that dream reports, at least when gathered under certain ideal reporting conditions, will be veridical
(Windt, 2013).
CONCLUSION
In conclusion, we can now name a short, non-exhaustive list of
desiderata for future research, focusing on new interdisciplinary
targets connecting the philosophy of mind and empirical dream
research:
• Isolating the property of minimal phenomenal selfhood
(MPS): Much more precise data on bodiless dreams are
urgently needed. I have hypothesized that the sense of
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Why are dreams interesting for philosophers?
selfhood seems to remain robust even in those asomatic
OBEs and bodiless dreams in which there is neither an
experience of motion in space nor goal-directed mental
activity.
◦ Can this hypothesis be supported by new data?
◦ How can dream research inform conceptual work about the
necessary and sufficient conditions for MPS?
•
• Describing the phenomenal unit of identification (UI): It has
been shown that existing empirical material on asomatic OBEs
fails to distinguish between cases in which the only locus of
identification is the minimal unit of an extensionless point
in space and cases in which it is the maximal unit (as in
parasomatic OBEs of the “pure consciousness” variant).
◦ Obviously, the same problem exists for bodiless dreams; new
questionnaires should be designed to resolve this ambiguity.
• Taxonomy: There is now a new way to categorize dreams,
namely, by their unit of identification (UI).
•
•
◦ How can questionnaires be optimized in order to reliably
pick out the UI, turning it into a new dimension in scientific
taxonomies of dreaming?
• Isolating the epistemic agent model (EAM): How can dream
researchers help to isolate the EAM in its purest form, and how
can it contribute to describing the transition from MPS to EAM
(e.g., in lucidity onset)?
• Dissociating functional levels of the first-person perspective
(1PP): Which specific contributions can dream research make
to the project of grounding the 1PP?
• 1PP and EAM: Is the “epistemicity” of the EAM a necessary
condition for the occurrence of a robust form of phenomenal
perspectivalness (1PP)?
◦ Is every conscious subject necessarily a (phenomenologically) knowing self, or should we treat the conjunction of
“transparency” and “self-location” in itself as a sufficient
condition?
• Lucidity and EAM: Is it really true that extended bodiless
dreams mostly occur in lucid dreams?
◦ Here, the falsifiable hypothesis is that a stable EAM is necessary to extend such dreams beyond brief, snapshot-like
episodes. More data are needed.
• Phenomenology: One empirical prediction the current proposal makes is that transparent spatiotemporal self-location is
necessary and sufficient for bringing about a minimal, consciously experienced sense of selfhood.
◦ Do we know any cases of phenomenally opaque self-location,
i.e., cases in which the location in a spatiotemporal frame of
reference is itself consciously experienced as a form of representational content, as something that is not directly given,
but as an internal construct? Is MPS instantiated in these
cases?
◦ Dissociating self-location and self-identification: Are there
fully lucid, phenomenally opaque, and bodiless dreams for
Frontiers in Psychology | Consciousness Research
•
which it is true that spatiotemporal self-location is itself
experienced as a form of (mis)representational content, but
in which the phenomenal dimension of self-identification is
not given?
Embodiment: The depth of embodiment during dreaming
should be investigated in greater detail, because it sheds
light on the different ways in which the body structures and
anchors the phenomenal, representational, and behavioral
spaces we navigate.
◦ Can the multiple cognitive deficits seen in the dream state
be better understood if we analyze them as functional
deficits in embodiment?
◦ How determinate (or indeterminate) is oneiric body representation?
Cognitive phenomenology: How can dream research
inform debates in philosophy of mind, for example by elucidating the hitherto neglected nature of the frequent, cyclical
recurrence of loss of mental self-control?
Mind wandering: What exactly is the relationship between
mental self-control, the occurrence of dream lucidity and
what researchers in mind wandering call “meta-awareness”?
◦ Can lucid lapses and mind-wandering lapses
plausibly be interpreted as the disintegration of
the EAM?
◦ Are there common positive functionalities connecting
dreaming and mind wandering during wake states, such
as the encoding of long-term memory, complex, preparatory motor planning, or creative incubation?
◦ False lucidity and the phenomenology of insight: In
becoming lucid and in daytime mind wandering, is
the experience of oneself having actively regained metaawareness (and thereby mental autonomy) an illusion
of control over a mental event that was really triggered
by an unconscious process? Are there other common
functionalities?
Epistemology: How can dream research inform technical
debates in philosophical epistemology, for instance though
the “argument from cognitive corruption” sketched above?
◦ What methodological consequences do such debates have
for dream research itself?
In conclusion, it has become clear that philosophers and dream
researchers still have a lot to learn from each other, and that
interdisciplinary cooperation should and must be further developed. In order to directly support this goal, the current contribution has tried to isolate a set of particularly promising
research targets and described specific interdisciplinary contact points. Viewed from the systematic, metatheoretical perspective of philosophy of mind, the MPS-problem may be the
most relevant and innovative entry point, because it helps
to conceptually unify the problem landscape in a new way.
Dreams and phenomenal states are subjective states, and in
order to understand the constitutive conditions determining
the gradual emergence of a subject of experience, we need
to understand the fundamental phenomenology of transparent self-identification that is common to all levels of conscious
subjectivity.
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Conflict of Interest Statement: The
Author, Editor and Chief Editor
declare that while the author Thomas
Metzinger and the editor J. Windt
are currently employed by the same
institution (Johannes GutenbergUniversität, Mainz, Germany) there
has been no conflict of interest during the review and handling of this
manuscript. The author declares that
the research was conducted in the
absence of any commercial or financial
relationships that could be construed
as a potential conflict of interest.
Received: 26 July 2013; accepted: 25
September 2013; published online: 31
October 2013.
Citation: Metzinger T (2013) Why are
dreams interesting for philosophers? The
example of minimal phenomenal selfhood, plus an agenda for future research.
Front. Psychol. 4:746. doi: 10.3389/fpsyg.
2013.00746
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