NOTES - The Ego Tunnel - Thomas Metzinger

The Ego Tunnel: The Science of the Mind and the Myth of the Self - Thomas Metzinger (2009)



1 M. Botvinick & J. Cohen, “Rubber Hand ‘Feels’ Touch That Eyes See,” Nature 391:756 (1998).

2 B. Lenggenhager et al., “Video Ergo Sum: Manipulating Bodily Self-Consciousness,” Science 317:1096-99 (2007). For a concise conceptual interpretation, see O. Blanke & T. Metzinger, “Full-body Illusions and Minimal Phenomenal Selfhood,” Trends Cog. Sci. 13(1):7-13 (2009).

3 “Transparency” is a technical term in the modern philosophy of mind; a conscious representation is transparent if the system using it cannot, by means of introspection alone, recognize it as a representation. As philosophers might say, we see only the content, never the carrier—only “intentional properties” are accessible to introspection. Subjectively, this creates the feeling of being in direct contact with reality.

4 Thomas Metzinger, Being No One: The Self-Model Theory of Subjectivity (Cambridge, MA: MIT Press, 2003). The shortest freely available summary can be found in Scholarpedia 2(10):4174, at; for overviews, see Metzinger, Précis of “Being No One,” Psyche 11(5):1-35 (2004), at; and Metzinger, “Empirical Perspectives from the Self-Model Theory of Subjectivity,” Progress in Brain Res. 168:215-246 (2008) (electronic offprint available from author).


1 See T. Metzinger, “Beweislast für Fleischesser,” Gehirn & Geist 5:70-75 (2006), reprinted in C. Könneker, Wer erklärt den Menschen? Hirnforscher, Psychologen und Philosophen im Dialog (Frankfurt am Main: Fischer, 2006); A. K. Seth et al., “Criteria for Consciousness in Humans and Other Mammals,” Consciousness and Cognition 14:119-139 (2005); and D. B. Edelman et al., “Identifying Hallmarks of Consciousness in Non-Mammalian Species,” Consciousness and Cognition 14:169-187 (2005). Octopi are particularly interesting, because their brain architecture is very different from that of mammals, but they turn out to be much smarter than was assumed in the past. Although cognitive complexity per se is not an argument for the existence of subjective experience, we now have evidence that makes at least primary consciousness quite plausible in octopi; see J. A. Mather, “Celaphod Consciousness: Behavioural Evidence,” Consciousness and Cognition 17:37-48 (2008).

2 See Patrick Wilken, “ASSC-10 Welcoming address,” in 10th Annual Meeting of the Association for the Scientific Study of Consciousness, 23-36 June 2006, Oxford, U.K., 6. At

3 See Thomas Metzinger, ed., Conscious Experience (Thorverton, UK, and Paderborn, Germany: mentis & Imprint Academic, 1995).

4 See the special issue on the neurobiology of animal consciousness in Consciousness and Cognition 14(1):1-232 (2005), in particular A. K. Seth et al., “Criteria for Consciousness in Humans and Other Mammals,” 119-139.

5 See Thomas Metzinger, ed., Neural Correlates of Consciousness: Empirical and Conceptual Questions (Cambridge, MA: MIT Press, 2000).

6 See Colin McGinn, “Can We Solve the Mind-Body Problem?” Mind 98:349-366 (1989). Reprinted in Ned Block et al., eds., The Nature of Consciousness: Philosophical Debates (Cambridge, MA: MIT Press, 1997); and Metzinger, “Introduction: Consciousness Research at the End of the Twentieth Century,” in Metzinger, ed., Neural Correlates of Consciousness (2000).

7 Antti Revonsuo, Inner Presence: Consciousness as a Biological Phenomenon (Cambridge, MA: MIT Press, 2006), 144ff.


1 In philosophical parlance, a “zombie” is a hypothetical entity that behaves exactly like a person and is objectively indistinguishable from one, but has no inner awareness of anything. If zombies were at least logically possible, this could perhaps show that there is no entailment from physical facts to facts about consciousness.

2 See, for example, Rocco J. Gennaro, ed., Higher-Order Theories of Consciousness: An Anthology (Philadelphia: John Benjamins, 2004); and David Rosenthal, Consciousness and Mind (New York: Oxford University Press, 2006).

3 See S. P. Vecera & K. S. Gilds, “What Is It Like to Be a Patient with Apperceptive Agnosia?” Consciousness and Cognition 6:237-266 (1997).

4 A. Marcel, “Conscious and Unconscious Perception: An Approach to the Relations Between Phenomenal Experience and Perceptual Processes,” Cog. Psychology 15:292 (1983).

5 See, for example, G. Tononi & G. M. Edelman, “Consciousness and Complexity,” Science 282:1846-51 (1998); and Tononi et al., “Complexity and the Integration of Information in the Brain,” Trends Cog. Sci. 2:44-52 (1998). For an exciting recent application to the difference between waking and sleeping, see M. Massimini et al., “Breakdown of Cortical Effective Connectivity During Sleep,” Science 309:2228-32 (2005). For a popular description, see Edelman and Tononi, A Universe of Consciousness: How Matter Becomes Imagination (New York: Basic Books, 2000).

6 Thomas Metzinger, Being No One: The Self-Model Theory of Subjectivity (Cambridge, MA: MIT Press, 2003).

7 In Greek mythology, the analogy between sleep and death was even closer: Hypnos, the god of sleep, and Thanatos, the god of death, were twins, the sons of Nyx, the night. Morpheus, the god of dreams, was Hypnos’ son. As in Shakespeare, to sleep, and possibly to die, is perchance to dream.

8 See V. A. F. Lamme, “Towards a True Neural Stance on Consciousness,” Trends Cog. Sci. 10(11):494-501 (2006); S. Dehaene et al., “Conscious, Preconscious, and Subliminal Processing: A Testable Taxonomy,” Trends Cog. Sci.10(5):204-211 (2006).

9 A. Lutz, “Changes in the Tonic High-Amplitude Gamma Oscillations During Meditation Correlates with Long-Term Practitioners’ Verbal Reports,” poster at the 9th ASSC conference, Pasadena, CA (2005); Lutz et al., “Long-Term Meditators Self-Induce High-Amplitude Synchrony During Mental Practice,” Proc. Nat. Acad. Sci. 101(46):16369-73 (2004). A good recent review is A. Lutz et al., “Attention Regulation and Monitoring in Meditation,” Trends Cog. Sci. 12(4):163-169 (2008).

10 Although I ultimately disagree with his theory of the “objective self,” perhaps the most beautiful and readable exposition of this problem and its application to self-consciousness can be found in chapter 4 of Thomas Nagel’s The View from Nowhere (New York: Oxford University Press, 1986).

11 R. L. Gregory, “Visual Illusions Classified,” Trends Cog. Sci. 1:190-194 (1997).

12 Ernst Pöppel, Mindworks: Time and Conscious Experience (New York: Harcourt Brace Jovanovich, 1988); E. Ruhnau, “Time-Gestalt and the Observer,” in Thomas Metzinger, ed., Conscious Experience (Thorverton, UK, and Paderborn, Germany: mentis & Imprint Academic, 1995).

13 R. M. Halsey & A. Chapanis, “Number of Absolutely Identifiable Hues,” Jour. Optical Soc. Amer. 41(12):1057-58 (1951). For an excellent philosophical discussion, see D. Raffman, “On the Persistence of Phenomenology,” in Thomas Metzinger, ed., Conscious Experience (Thorverton, UK, and Paderborn, Germany: mentis & Imprint Academic, 1995).

14 Raffman, “On the Persistence of Phenomenology,” 295 (1995).

15 Clarence I. Lewis, Mind and the World Order (New York: Scribner’s, 1929). See also Daniel C. Dennett, “Quining Qualia,” in A. J. Marcel & E. Bisiach, Consciousness in Contemporary Science (New York: Oxford University Press, 1988).

16 Diana Raffman, Language, Music, and Mind (Cambridge, MA: MIT Press, 1993).

17 P. Churchland, “Eliminative Materialism and the Propositional Attitudes,” Jour. Phil. 78(2):67-90 (1981).

18 Quoted after the extensively revised 1991 edition by M. David Enoch and Hadrian N. Ball, Uncommon Psychiatric Syndromes (London: Butterworth-Heinemann, 1991), 167.

19 I am grateful to Dr. Richard Chapman of the University of Utah’s Pain Research Center for pointing out to me the concept of an “immunculus”: the network of natural autoantibodies targeting extracellular, membrane, cytoplasmic, and nuclear self-antigens. The repertoires of natural autoantibodies are surprisingly constant in healthy persons and, independently of gender and age, are characterized by only minimal individual variations.


1 M. Botvinick & J. Cohen, “Rubber Hand ‘Feels’ Touch That Eyes See,” Nature 391:756 (1998).

2 K. C. Armel & V. S. Ramachandran, “Projecting Sensations to External Objects: Evidence from Skin Conductance Response,” Proc. Roy. Soc. Lond. 270:1499-1506 (2003).

3 M. R. Longo et al., “What Is Embodiment? A Psychometric Approach,” Cognition 107:978-998 (2008).

4 See Antonio Damasio, The Feeling of What Happens: Body, Emotion, and the Making of Consciousness (London: Vintage, 1999), 19. See also A. D. Craig, “How Do You Feel? Interoception: The Sense of the Physiological Condition of the Body,” Nat. Rev. Neurosci. 3:655-666 (2002) and “Interoception: The Sense of the Physiological Condition of the Body,” Curr. Opin. Neurobiol. 13:500-505 (2003).

5 For an excellent recent review—including a new, empirically informed synthesis—of the classical intuition of David Hume (that the self is just a bundle of impressions and everything can be explained “bottom-up”) as opposed to the classical Kantian intuition (self-consciousness is a necessary prior condition for experiencing the body as a whole and everything must be explained “top-down”), see F. De Vignemont et al., “Body Mereology,” in Günther Knoblich et al., eds., Human Body Perception from the Inside Out (New York: Oxford University Press, 2006).

6 The terminology was never entirely clear, but it frequently differentiated between an unconscious “body schema” and a conscious “body image.” The body schema (a notion introduced in 1911 by Sir Henry Head and Gordon Holmes, two British neurologists) would be a functional entity, providing an organized model of the bodily self in the brain, whereas the body image would also include our conscious perceptions of our own body as well as thoughts about and attitudes toward it. For a philosophical perspective on the conceptual confusion surrounding both notions, see Shaun Gallagher, How the Body Shapes the Mind (New York: Oxford University Press, 2005). For an excellent review of the empirical literature, see A. Maravita, “From ‘Body in the Brain’ to ‘Body in Space’: Sensory and Intentional Components of Body Representation,” in Knoblich et al., Human Body Perception (2006).

7 A. Maravita & A. Iriki, “Tools for the Body (Schema),” Trends Cog. Sci. 8:79-86 (2004). An excellent recent overview is A. Iriki & O. Sakura, “The Neuroscience of Primate Intellectual Evolution: Natural Selection and Passive and Intentional Niche Construction,” Phil. Trans. R. Soc. B 363:2229- 41 (2008).

8 See A. Iriki et al., “Coding of Modified Body Schema During Tool-Use by Macaque Post-Central Neurons,” Neuroreport 7:2325-30 (1996); and Maravita & Iriki, “Tools for the Body (Schema)” (2004).

9 J. M. Carmena et al., “Learning to Control a Brain-Machine Interface for Reaching and Grasping by Primates,” PLoS Biology 1:193-208 (2003).

10 Here is how Iriki and Sakura put this important point: “If external objects can be reconceived as belonging to the body, it may be inevitable that the converse reconceptualization, i.e., the subject can now objectify its body parts as equivalent to external tools, becomes likewise apparent. Thus, tool use may lead to the ability to disembody the sense of the literal flesh-and-blood boundaries of one’s skin. As such, it might be precursorial to the capacity to objectify the self. In other words, tool use might prepare the mind for the emergence of the concept of the meta-self, which is another defining feature of human intelligence.” See Iriki & Sakura, “The Neuroscience of Primate Intellectual Evolution,” 2232 (2008).

11 See O. Blanke & T. Metzinger, “Full-Body Illusions and Minimal Phenomenal Selfhood,” Trends Cog. Sci. 13(1):7-13 (2009).

12 See T. Metzinger, “Out-of-Body Experiences as the Origin of the Concept of a ‘Soul,’” Mind and Matter 3(1):57-84 (2005).

13 E. R. S. Mead, The Doctrine of the Subtle Body in Western Tradition (London: John M. Watkins, 1919).

14 It is important to be clear about the potential ontological conclusions: Even if a fully reductive explanation of all subtypes of OBEs should be achieved—and even if my hypothesis about the history of the concept of a soul is correct—it still remains logically possible that souls do exist. True, we would no longer need the concept of a soul for the purposes of science or philosophy; it would no longer figure in any rational, data-driven theory about the human mind. Logical possibility is something very weak, but it is hard to prove the nonexistence of something, and it always remains possible that one day we will discover a new sense in which the soul is not an empty concept at all.

15 It is interesting to note how the earliest historical meaning of the word “information” in English was the act of informing, or giving form or shape to the mind. What I call the “self-model” is exactly this: the “inner form” an organism gives to itself, the shaping of a mind.

16 Susan J. Blackmore, Beyond the Body: An Investigation of Out-of-the-Body Experiences (London: Granada, 1982).

17 In addition to Beyond the Body, see S. Blackmore, “A Psychological Theory of the Out-of-Body Experience,” Jour. Parapsychol. 48:201-218 (1984); and S. J. Blackmore, “Where Am I? Perspectives in Imagery and the Out-of-Body Experience,” Jour. Mental Imagery 11:53-66 (1987).

18 E. Waelti, Der dritte Kreis des Wissens (Interlaken: Ansata, 1983), 18, 25. English translation by T. Metzinger.

19 C. S. Alvarado, “Out-of-Body Experiences,” in E. Cardeña et al., eds., Varieties of Anomalous Experience: Examining the Scientific Evidence (Washington, DC: American Psychological Association, 2000).

20 See, for example, J. Palmer, “A Community Mail Survey of Psychic Experience,” Jour. Am. Soc. Psychical Res. 73:21-51 (1979); S. Blackmore, “A Postal Survey of OBEs and Other Experiences,” Jour. Soc. Psychical Res.52:225-244 (1984).

21 See Alvarado, “Out-of-Body Experiences” (2000) for an overview of many studies; Blackmore, “Spontaneous and Deliberate OBEs: A Questionnaire Survey,” Jour. Soc. Psychical Res. 53:218-224 (1986); Harvey J. Irwin, Flight of Mind (Metuchen, NJ: Scarecrow Press, 1985), 174 ff; O. Blanke & C. Mohr, “Out-of-Body Experience, Heautoscopy, and Autoscopic Hallucination of Neurological Origin: Implications for Neurocognitive Mechanisms of Corporeal Awareness and Self Consciousness,” Brain Res. Rev. 50:184-199 (2005).

22 O. Devinsky et al., “Autoscopic Phenomena with Seizures,” Arch. Neurol. 46:1080-8 (1989).

23 See, for example, P. Brugger, “Reflective Mirrors: Perspective-Taking in Autoscopic Phenomena,” Cog. Neuropsychiatry 7:179-194 (2002); Brugger et al., “Unilaterally Felt Presences: The Neuropsychiatry of One Invisible Doppelgänger,” Neuropsychiatry, Neuropsychology, and Behavioral Neurology 9:114-122 (1996); Brugger et al., “Illusory Reduplication of One’s Own Body: Phenomenology and Classification of Autoscopic Phenomena,” Cog. Neuropsychiatry 2:19-38 (1997); Devinsky et al., “Autoscopic Phenomena” (1989).

24 U. Wolfradt, “Außerkörpererfahrungen (AKE) aus differentiellpsychologischer Perspektive,” Zeitschrift f. Paraps. u. Grenzgeb. D. Psych. 42/43:65-108 (2000/2001); U. Wolfradt & S. Watzke, “Deliberate Out-of-Body Experiences, Depersonalization, Schizotypal Traits, and Thinking Styles,” Jour. Amer. Soc. Psychical Res. 93:249-257 (1999).

25 H. J. Irwin, “The Disembodied Self: An Empirical Study of Dissociation and the Out-of-Body Experience,” Jour. Parapsych. 64(3):261- 277 (2000).

26 See Wolfradt, “Außerkörpererfahrungen (AKE)” (2000/2001).

27 Ibid. Other studies find only 22-36 percent; see Alvarado, “Out-of-Body Experiences” (2000).

28 Wolfradt, “Außerkörpererfahrungen” (2000/2001).

29 C. Green, Out-of-the-Body Experiences (London: Hamish Hamilton, 1968).

30 O. Blanke et al., “Stimulating Illusory Own-Body Perceptions,” Nature 419:269-270 (2002).

31 For a more detailed hypothesis concerning the role of the temporoparietal junction, see Blanke et al., “Out-of-Body Experience and Autoscopy of Neurological Origin,” Brain 127:243-258 (2004); S. Bünning & O. Blanke, “The Out-of-Body Experience: Precipitating Factors and Neural Correlates,” Prog. Brain Res. 150:333-353 (2005); O. Blanke & S. Arzy, “The Out-of-Body Experience: Disturbed Self-Processing at the Temporo-Parietal Junction,” The Neuroscientist 11:16-24 (2005); and F. Tong, “Out-of-Body Experiences: From Penfield to Present,” Trends Cog. Sci. 7:104-106 (2003).

32 Blanke et al., “Linking Out-of-Body Experience and Self-Processing to Mental Own-Body Imagery and the Temporoparietal Junction,” Jour. Neurosci. 25:550-557 (2005).

33 For more on this point, see Blanke & Metzinger, “Full-Body Illusions and Minimal Phenomenal Selfhood,” 13(1):7-13 (2009).

34 See Wolfradt, “Außerkörpererfahrungen (AKE)” (2000/2001), 91.

35 Can you imagine what it would be like to look at yourself from the outside and shake your own hand? Henrik Ehrsson of the Karolinska Institute in Stockholm, Sweden, is one of the leading figures in self-model research. He created one of the classic full-body illusion experiments and also demonstrated that upper limb amputees can be induced to experience a rubber hand as their own and extended the field by focusing on behavioral and neuroimaging evidence. Recently, members of his team managed to not only trigger the illusion that another person’s body was one’s own, but also create the phenomenal experience of being in that other person’s body while actually facing their own body and shaking their own hand. See Valerie I. Petrovka & H. Henrik Ehrsson, “If I Were You: Perceptual Illusion of Body Swapping,” PLoS ONE 3(12):e3832 (2008), H. Henrik Ehrsson, “The Experimental Induction of Out-of-Body Experiences,” Science 3127:1048 (2007), H. Henrik Ehrsson et al., “Upper Limb Amputees Can Be Induced to Experience a Rubber Hand as their Own,” Brain 131:3443-3452; Tamar R. Makin et al., “On the Other Hand: Dummy Hands and Peripersonal Space,” Beh. Brain. Res. 191:1-10 (2008).

36 See W. Barfield et al., “Presence and Performance Within Virtual Environments,” in Woodrow Barfield & Thomas A. Furness III, eds., Virtual Environments and Advanced Interface Design (New York: Oxford University Press, 1995). See also M. V. Sanchez-Vives & M. Slater, “From Presence to Consciousness Through Virtual Reality,” Nat. Rev. Neur. 6.332- 339 (2005). Mel Slater, for many years a leading researcher in the field of virtual reality, has recently demonstrated that the feeling of ownership can also be induced for simulated body parts in virtual environments (rather than, as in our experiment, having people still look at their “real” body). Obviously, this permits experiments that would never have been possible in the physical world, including real-time modifications of virtual bodies not only in terms of length, size, and appearance, but also complex motion patterns. As the authors put it: “For the future our work also suggests that people can have their ‘self ’ enter the virtual domain in a genuine sense of the word, and not just metaphorically as in current day computer games and online communities. In combination with BCI [brain-computer interfaces] we envisage a functioning virtual body that is felt as their own by participants, with a significant application in VR training, limb prosthetics, and entertainment.” See M. Slater et al., “Towards a Digital Body: The Virtual Arm Illusion,” Frontiers Hum. Neurosci. 2:6. doi:10.3389/neuro.09.006.2008.

37 See

38 See, for example, R. A. Sherman et al., “Chronic Phantom and Stump Pain Among American Veterans: Results of a Survey,” Pain 18:83-95 (1984).

39 S. W. Mitchell, “Phantom Limbs,” Lippincott’s Mag. Pop. Lit. & Sci. 8:563-569 (1871).

40 See V. S. Ramachandran et al., “Scientific Correspondence: Touching the Phantom Limb,” Nature 377:489-490 (1995); V. S. Ramachandran & D. Rogers-Ramachandran, “Synaesthesia in Phantom Limbs Induced with Mirrors,” Proc. Roy. Soc. Lond. B:377-386 (1996); and V. S. Ramachandran & Sandra Blakeslee, Phantoms in the Brain (New York: William Morrow, 1998).

41 V. S. Ramachandran, “Consciousness and Body Image: Lessons from Phantom Limbs, Capgras Syndrome and Pain Asymbolia,” Phil. Trans. Roy. Soc. Lond. B353:1851-9 (1998). For clinical and experimental details, see Ramachandran and Rogers-Ramachandran, “Synaesthesia in Phantom Limbs” (1996).

42 P. Brugger et al., “Beyond Re-membering: Phantom Sensations of Congenitally Absent Limbs,” Proc. Nat. Acad. Sci. USA 97:6167-72 (2000).

43 See § 12 and § 13 of The Ethics.


1 Adapted from the case report of a sixty-eight-year-old woman suffering from stroke-related, transient alien hand syndrome. From D. H. Geschwind et al., “Alien Hand Syndrome: Interhemispheric Disconnection Due to Lesion in the Midbody of the Corpus Callosum,” Neurology 45:802-808 (1995).

2 See K. Goldstein, “Zur Lehre der Motorischen Apraxie,” Jour. für Psychologie und Neurologie 11:169-187 (1908); W. H. Sweet, “Seeping Intracranial Aneurysm Simulating Neoplasm,” Arch. Neurology & Psychiatry 45:86-104 (1941); S. Brion & C.-P. Jedynak, “Troubles du Transfert Interhémisphérique (Callosal Disconnection). A Propos de Trois Observations de Tumeurs du Corps Calleux. Le Signe de la Main Étrangère,” Revue Neurologique 126:257-266 (1972); G. Goldberg et al., “Medial Frontal Cortex Infarction and the Alien Hand Sign,” Arch. Neurology 38:683-686 (1981). For an important new conceptual distinction, see C. Marchetti & S. Della Sala, “Disentangling the Alien and the Anarchic Hand,” Cog. Neuropsychiatry 3:191-207 (1998).

3 Goldberg et al., “Medial Frontal Cortex Infarction,” 684 (1981).

4 G. Banks et al., “The Alien Hand Syndrome: Clinical and Postmortem Findings,” Arch. Neurology 46:456-459 (1989).

5 Ibid.

6 For more on the representational architecture of volition and akinetic mutism, see T. Metzinger, “Conscious Volition and Mental Representation: Towards a More Fine-Grained Analysis,” in Natalie Sebanz & Wolfgang Prinz, eds., Disorders of Volition (Cambridge, MA: MIT Press, 2006).

7 S. Kremer et al., Letter to the Editor, “The Cingulate Hidden Hand,” Jour. Neurology, Neurosurgery, and Psychiatry 70:264-265 (2001); see also a classical study by I. Fried et al., “Functional Organization of Human Supplementary Motor Cortex Studied by Electrical Stimulation,” Jour. Neurosci. 11:3656-66 (1991). In this study, subjects stimulated with electrical currents of different strength reported the illusory conscious perception of ongoing movement, or the anticipation of movement, or the “urge” to perform a movement, all “in the absence of overt motor activity.”

8 D. M. Wegner & T. Wheatley, “Apparent Mental Causation: Sources of the Experience of Will,” Amer. Psychol. 54(7):480-492 (1999).

9 Wegner & Wheatley, “Apparent Mental Causation” (1999), 488.

10 Ibid., 483.

11 See, for instance, P. Haggard, “Conscious Awareness of Intention and of Action,” in Johannes Rössler & Naomi Eilan, eds., Agency and Self-Awareness—Issues in Philosophy and Psychology (Oxford, UK: Clarendon Press, 2003). A good recent review is Patrick Haggard, “Human Volition: Towards a Neuroscience of Will,” Nat. Rev. Neurosci. 9:934-946 (2008).

12 It is true that indeterminacy exists on the subatomic level, but the mind cannot somehow sneak into the physical world through indeterminate quantum processes. (Nor is chance what we want: Philosophically, randomness in the brain would be just as bad as full determination.) Quantum theories of free will are empirically false as well: There may be different kinds of brains somewhere else in the universe, but in human brains the firing of neurons and so on take place on the macroscopic scale. For such huge objects as nerve cells at 37°C body temperature, quantum events simply play no role.

13 The voluntary inhibition of voluntary actions seems to be mostly determined by unconscious events in the anterior median cortex. See M. Brass & P. Haggard, “To Do or Not To Do: The Neural Signature of Self-Control,” J. Neurosci. 27:9141-9145. (2007).

14 See T. Metzinger, “The Forbidden Fruit Intuition,” The Edge Annual Question—2006: What Is Your Dangerous Idea? Reprinted in J. Brockman, ed., What Is Your Dangerous Idea? Todays’s Leading Thinkers on the Unthinkable (New York: HarperPerennial, 2007), 153-155.

15 It would not be a new thought in the history of philosophy. Vasubandhu, a fourth-century Buddhist teacher and one of the most important figures in the development of Mahayana Buddhism in India, reports: Buddha has spoken thus: ‘O, Brethren! actions do exist, and also their consequences (merit and demerit), but the person that acts does not. There is no one to cast away this set of elements and no one to assume a new set of them. (There exists no individual), it is only a conventional name given to (a set) of elements.’ Appendix to the VIIIth chapter of Vasubandhu’s Abhidarmakoça, §9: 100.b.7; quoted after T. Stcherbatsky, “The Soul Theory of the Buddhists,” Bull. Acad. Sci. Russ. 845 (1919).


1 The second question, of course, is the one Descartes asked in the first Meditation, when he realized that everything he had ever believed to be certain—including his impression of sitting by the fire in his winter coat and closely inspecting the piece of paper in his hands—could equally well have occurred in a dream. What makes the problem of dream skepticism so intractable is that even in a “best-case scenario” of sensory perception, there is apparently no reliable, fool-proof method of distinguishing wakefulness and dreaming. According to dream skepticism, literally all of our experiences of waking life could be nothing more than a dream, and we are unable, even in principle, ever to decide this question with certainty. For a detailed discussion of the problem of dream skepticism, see, for instance, Barry Stroud, The Significance of Philosophical Scepticism (New York: Oxford University Press, 1984). For the status of the phenomenal and the epistemic subject in the dream state, see J. Windt & T. Metzinger, “The Philosophy of Dreaming and Self-Consciousness: What Happens to the Experiential Subject During the Dream State?” in Patrick McNamara & Deirdre Barrett, eds., The New Science of Dreaming (Westport, CT: Praeger, 2007). See

2 See J. A. Hobson et al., “Dreaming and the Brain: Toward a Cognitive Neuroscience of Conscious States,” Behavioral and Brain Sci. 23:793-842 (2000); and Antti Revonsuo, Inner Presence: Consciousness as a Biological Phenomenon (Cambridge, MA: MIT Press, 2006).

3 Helen Keller, The World I Live In (New York: New York Review Books, 2003).

4 H. Bertolo et al., “Visual Dream Content, Graphical Representation and EEG Alpha Activity in Congenitally Blind Subjects,” Cog. Brain Res. 15:277- 284 (2003).

5 See C. H. Schenck, “Violent Moving Nightmares,”; E. J. Olson et al., “Rapid Eye Movement Sleep Behaviour Disorder: Demographic, Clinical, and Laboratory Findings in 93 Cases,” Brain 123:331- 339 (2000); and C. H. Adler & M. J. Thorpy, “Sleep Issues in Parkinson’s Disease,” Neurology 64 (suppl. 3):12-20 (2005).

6 See Hobson et al., “Dreaming and the Brain” (2000) for details.

7 F. van Eeden, “A Study of Dreams,” Proc. Soc. Psychical Res. 26:431-461 (1913).

8 Oliver Fox, Astral Projection (New Hyde Park, NY: University Books, 1962). Also quoted in S. LaBerge & J. Gackenbach, “Lucid Dreaming,” in Etzel Cardeña et al., eds., Varieties of Anomalous Experience: Examining the Scientific Evidence (Washington, DC: American Psychological Association, 2000).

9 See Paul Tholey, Schöpferisch träumen (Niedernhausen, Ger.: Falken Verlag, 1987).

10 See Stephen LaBerge & Howard Rheingold, Exploring the World of Lucid Dreaming (New York: Ballantine, 1990).

11 S. LaBerge et al., “Lucid Dreaming Verified by Volitional Communication During REM Sleep,” Perceptual and Motor Skills 52:727-732 (1981); and S. LaBerge et al., “Psychophysiological Correlates of the Initiation of Lucid Dreaming,” Sleep Res. 10:149 (1981).

12 For details, see P. Garfield, “Psychological Concomitants of the Lucid Dream State,” Sleep Res. 4:183 (1975); S. LaBerge, “Induction of Lucid Dreams,” Sleep Res. 9:138 (1980); S. LaBerge, “Lucid Dreaming as a Learnable Skill: A Case Study,” Perceptual and Motor Skills 51:1039-41 (1980); LaBerge & Rheingold, Exploring the World of Lucid Dreaming (1990); and G. S. Sparrow, “Effects of Meditation on Dreams,” Sundance Comm. Dream Jour.1:48-49 (1976).

13 Hobson et al., “Dreaming and the Brain” (2000), 837. For details on the relation between the DLPFC and reflective thought, see A. Muzur et al., “The Prefrontal Cortex in Sleep,” Trends Cog. Sci. 6:475-481 (2002).

14 Tholey, Schöpferisch träumen (1987), 97. English translation by T. Metzinger.

15 “Spandrels” refers to Stephen Jay Gould and Richard C. Lewontin’s 1979 essay “The Spandrels of San Marco and the Panglossian Paradigm,” in which, using the architectural analogy, the authors argue that some biological features are exaptations: that is, currently used for something other than what they were “developed for” during natural selection. Proc. Royal Soc. London, Ser. B, Biol. Sci. (1934-1990) 205(1161):581-598 (September 21, 1979).


1 For details, see G. Rizzolatti et al., “From Mirror Neurons to Imitation: Facts and Speculations,” in Andrew N. Meltzoff & Wolfgang Prinz, eds., The Imitative Mind: Development, Evolution, and Brain Bases (Cambridge: Cambridge University Press, 2002); and G. Rizzolatti & M. Gentilucci, “Motor and Visual-Motor Functions of the Premotor Cortex,” in Pasko Rakic & Wolf Singer, eds., Neurobiology of Neocortex (New York: John Wiley & Sons, 1988). An excellent recent overview is Giacomo Rizzolatti & Corrado Sinigaglia, Mirrors in the Brain: How Our Minds Share Actions and Emotions (Oxford: Oxford University Press, 2008).

2 The mirror-neuron system may occasionally go awry. Patients suffering from a rare but well-known neurological syndrome called echopraxia are inevitably forced to act out any behavior they observe in other human beings. What likely happens in these patients is that the mirror-neuron system is inadvertently coupled to the motor system because of lack of prefrontal inhibition. Your mirror neurons come online and lose their ordinary status as purely offline simulators. Therefore, you are literally driven by the actions you see other people performing.

3 See V. Gallese & A. Goldman, “Mirror Neurons and the Simulation Theory of Mind-Reading,” Trends Cog. Sci. 2:493-501 (1998); M. Iacoboni et al., “Cortical Mechanisms of Imitation,” Science 268:2526-8 (1999); and V. Gallese, “The ‘Shared Manifold’ Hypothesis: From Mirror Neurons to Empathy,” Jour. Consciousness Studies 8:33-50 (2001).

4 See T. Metzinger & V. Gallese, “The Emergence of a Shared Action Ontology: Building Blocks for a Theory,” in G. Knoblich et al., eds., Self and Action. Special issue of Consciousness & Cognition 12(4):549-571 (2003).

5 V. Gallese, “Intentional Attunement: A Neurophysiological Perspective on Social Cognition and Its Disruption in Autism,” Brain Res. 1079:15-24 (2006); F. de Vignemont & T. Singer, “The Empathic Brain: How, When, and Why?” Trends Cog. Sci. 10:435-441 (2006).

6 L. Carr et al., “Neural Mechanisms of Empathy in Humans: A Relay from Neural Systems for Imitation to Limbic Areas,” Proc. Nat. Acad. Sci. USA 100(9):5497-5502 (2003); see also A. Goldman & C. S. Sripada, “Simulationist Models of Face-Based Emotion Recognition,” Cognition 94:193-213 (2005).

7 A. D. Lawrence et al., “Selective Disruption of the Recognition of Facial Expressions of Anger,” NeuroReport 13(6):881-884 (2002).

8 I. Morrison et al., “Vicarious Responses to Pain in Anterior Cingulate Cortex: Is Empathy a Multisensory Issue?” Cog. Affec. & Behav. Neuroscience 4:270-278 (2004); P. L. Jackson et al., “How Do We Perceive the Pain of Others: A Window into the Neural Processes Involved in Empathy,” NeuroImage 24:771-779 (2005); M. Botvinick et al., “Viewing Facial Expressions of Pain Engages Cortical Areas Involved in the Direct Experience of Pain,” NeuroImage 25:315-319 (2005).

9 This was the step from what I call second-order embodiment to third-order embodiment. In order to counteract the semantic inflation of the term “embodiment,” I have introduced the notions of “first-order embodiment” (the bottom-up self-organization of intelligent behavior avoiding explicit computation and relying only on physical properties of the system), “second-order embodiment” (generating intelligent behavior by using an integrated representation of the body as a whole, by internally representing oneself as embodied), and “third-order embodiment” (the functional elevation of second-order embodiment to the level of global availability, i.e., the conscious experience of embodiment). A short summary can be found in Scholarpedia 2 (10):4174 (2007) at

10 V. Gallese, “Embodied Simulation: From Neurons to Phenomenal Experience,” Phen. Cog. Sci. 4:23-38 (2005).

11 Gallese calls this specific phenomenal state “intentional attunement”—the peculiar experiential quality of familiarity with other individuals that arises because we implicitly match their intentions with processes that go on in our own brain when we form such intentions.

12 See T. Metzinger, “Self Models,” Scholarpedia 2(10):4174 (2007) at; and Metzinger, “Empirical Perspectives from the Self-Model Theory of Subjectivity,” Progress in Brain Res.168:215-246 (2008).

13 See W. B. Carpenter, Principles of Mental Physiology (London: Routledge, 1875). For a review, see H. Richter, “Zum Problem der ideomotorischen Phänomene,” Zeit. für Psychologie 71:161-254 (1957).

14 T. Lipps, “Einfühlung, innere Nachahmung und Organempfindung,” Arch. der Psychologie 1:185-204 (1903).

15 See G. Rizzolatti & Laila Craighero, “The Mirror-Neuron System,” Ann. Rev. Neurosci. 27:169-192 (2004); the classical paper is Rizzolatti & M. A. Arbib, “Language Within Our Grasp,” Trends Neurosci. 21:188-194 (1998). For a brief first overview, see Rizzolatti & Destro, “Mirror Neurons,” Scholarpedia 3(1):2055 (2008).

16 See Rizzolatti & Destro, “Mirror Neurons”;

17 See Gallese, “The ‘Shared Manifold’ Hypothesis” (2001), for an additional discussion, see pp. 174 of this book.

18 Jerome S. Bruner, Acts of Meaning (Cambridge, MA: Harvard University Press, 1990), 40.



2 A. Cleeremans, “Computational Correlates of Consciousness,” Prog. Brain Res. 150:81-98 (2005). See also his “Consciousness: The Radical Plasticity Thesis,” Prog. Brain Res. 168:19-33 (2008).

3 J. Bongard et al., “Resilient Machines Through Continuous Self-Modeling,” Science 314:1118-21 (2006).

4 Ibid. In particular, see also free online support material at (See for additional online material.)

5 See also Thomas Metzinger, “Empirical Perspectives from the Self-Model Theory of Subjectivity: A Brief Summary with Examples,” in Rahul Banerjee & Bikas K. Chakrabarti, eds., Progress in Brain Research (Amsterdam: Elsevier, 2008) 168:215-246. DOI: 10.1016/S0079- 6123(07)68018-2.

6 Karl Popper & J. C. Eccles, The Self and Its Brain: An Argument for Interactionism (New York: Routledge, 1984), 208. Alan M. Turing’s paper is in Mind 59:433-460 (1950).

7 It is interesting to note how perhaps the foremost theoretical “blind spot” of current philosophy of mind is conscious suffering. Thousands of pages have been written about color qualia and zombies, but almost no theoretical work is devoted to ubiquitous phenomenal states such as physical pain, boredom, or the everyday sadness known as subclinical depression. The same is true of panic, despair, shame, the conscious experience of mortality, and the phenomenology of losing one’s dignity. Why are these forms of conscious content generally ignored by the best of today’s philosophers of mind? Is it simple careerism (“Nobody wants to read too much about suffering, no matter how insightful and important the arguments are”), or are there deeper, evolutionary reasons for this cognitive scotoma? When one examines the ongoing phenomenology of biological systems on our planet, the varieties of conscious suffering are at least as dominant as, say, the phenomenology of color vision or the capacity for conscious thought. The ability to consciously see color appeared only very recently, and the ability to consciously think abstract thoughts of a complex and ordered form arose only with the advent of human beings. Pain, panic, jealousy, despair, and the fear of dying, however, appeared millions of years earlier and in a much greater number of species.


1 Our belief in invisible persons may have different roots, possibly including so-called hyperactive agent-detection devices (see D. Barrett, “Exploring the Natural Foundations of Religion,” Trends Cog. Sci. 4:29-34, 2000) and ancestor cults: See Daniel C. Dennett, Breaking the Spell: Religion as a Natural Phenomenon (New York: Viking, 2006), esp. 109ff; and Thomas Metzinger, Being No One: The Self-Model Theory of Subjectivity (Cambridge, MA: MIT Press, 2003), 371ff. Also note that out-of-body experiences would almost inevitably have contributed to early humankind’s firm belief in the existence of invisible persons and more subtle levels of reality. See T. Metzinger, “Out-of-Body Experiences as the Origin of the Concept of a ‘Soul,’” Mind and Matter 3(1):57-84 (2005).


1 Y. Kamitami & S. Shimojo, “Manifestation of Scotomas Created by Transcranial Magnetic Stimulation of Human Visual Cortex,” Nature Neuroscience 2:767-771 (1999).

2 B.-P. Bejjani et al., “Transient Acute Depression Induced by High-Frequency Deep-Brain Stimulation,” N.E. Jour. Med. 340:1476-80 (1999). Here are examples of how the patient described her own conscious experience: “I’m falling down in my head, I no longer wish to live, to see anything, hear anything, feel anything.” The authors report that when she was asked why she was crying and if she felt pain, she responded: “No, I’m fed up with life, I’ve had enough… . I don’t want to live anymore, I’m disgusted with life… . Everything is useless, always feeling worthless, I’m scared in this world.” When asked why she was sad, she replied: “I’m tired. I want to hide in a corner… . I’m crying over myself, of course… . I’m hopeless, why am I bothering you.” Note that deep brain stimulation can also have just the opposite effect, namely, relief from serious, treatment-resistant depression. Here is a description: “All patients spontaneously reported acute effects including ‘sudden calmness or lightness,’ ‘disappearance of the void,’ ‘sense of heightened awareness,’ ‘connectedness,’ and sudden brightening of the room, including a sharpening of visual details and intensification of colors in response to stimulation.” See H. Mayberg, “Clinical Study: Deep Brain Stimulation for Treatment-Resistant Depression,” Neuron 45:651-660 (2005).

3 C. M. Cook & M. A. Persinger, “Experimental Induction of the ‘Sensed Presence’ in Normal Subjects and an Exceptional Subject,” Percept. Mot. Skills 85:683-693 (1997). For a critical assessment and self-experiential report, see John Horgan, Rational Mysticism: Dispatches from the Border Between Science and Spirituality (New York: Houghton Mifflin, 2003).

4 See M. A. Persinger, “Religious and Mystical Experiences as Artifacts of Temporal Lobe Function: A General Hypothesis,” Perc. Mot. Skills 57:1255-62 (1983). Clinicians have long observed a deepening of emotionality plus the development of a serious, highly ethical and spiritual demeanor in certain patients with chronic mesial temporal lobe epilepsy. Whether this can count as evidence for a specific kind of “personality syndrome” is still disputed. See O. Devinsky & S. Najjar, “Evidence Against the Existence of a Temporal Lobe Epilepsy Personality Syndrome,” Neurology 53:S13-S25 (1999); D. Blume, “Evidence Supporting the Temporal Lobe Epilepsy Personality Syndrome,” Neurology 53:S9-S12 (1999).

5 For more information, see the Web portal my collaborators Carsten Griesel and Elisabeth Hildt have created at

6 B. Maher, “Poll Results: Look Who’s Doping,” Nature 452:674-675 (2008). See also B. Sakhanian & S. Morein-Zamir, “Professor’s Little Helper,” Nature 450:1157-5 (2007).

7 M. J. Farah et al., “Neurocognitive Enhancement: What Can We Do and What Should We Do?” Nature Reviews Neuroscience 5:421-425 (2004). Four years later, after a careful analysis of pros and cons and perhaps surprisingly to many, leading figures in neuroethics are now coming to the conclusion that “We should welcome new methods of improving our brain function. In a world in which human workspans and lifespans are increasing, cognitive enhancement tools—including the pharmacological—will be increasingly useful for improved quality of life and extended work productivity, as well as to stave off normal and pathological accerelated cognitive declines. Safe and effective cognitive enhancers will benefit both the individual and society.” See H. Greely et al., “Towards Responsible Use of Cognitive-Enhancing Drugs by the Healthy,” Nature 456:702-705 (2008).

8 For a first and careful discussion of this important question, see T. Douglas, “Moral Enhancement,” J. Appl. Phil. 25:228-245 (2008).

9 Alexander Shulgin and Ann Shulgin, PiHKAL: A Chemical Love Story (Transform Press, 1991); and Alexander Shulgin, TiHKAL: The Continuation (Transform Press, 1997).

10 W. N. Pahnke & W. A. Richards, “Implications of LSD and Experimental Mysticism,” Jour. Religion & Health 5:179 (1966).

11 R. R. Griffiths et al., “Psilocybin Can Occasion Mystical-Type Experiences Having Substantial and Sustained Personal Meaning and Spiritual Significance,” Psychopharm. 187:268-283 (2006).

12 R. R. Griffiths et al., “Mystical-Type Experiences Occasioned by Psilocybin Mediate the Attribution of Personal Meaning and Spiritual Significance 14 Months Later,” Jour. Psychopharm. 22:621-632 (2008).

13 N. Malleson, “Acute Adverse Reactions to LSD in Clinical and Experimental Use in the United Kingdom,” Br. Jour. Psychiatry 118:229-230 (1971).

14 S. Cohen, “Lysergic Acid Diethylamide: Side Effects and Complications,” Jour. Nerv. Ment. Dis. 130:30-40 (1960).

15 See R. J. Strassman, “Adverse Reactions to Psychedelic Drugs: A Review of the Literature,” Jour. Nerv. Men. Dis. 172:577-595 (1984); J. H. Halpern & H. G. Pope, “Do Hallucinogens Cause Residual Neuropsychological Toxicity?” Drug Alcohol Depend. 53:247-256 (1999); M. W. Johnson et al., “Human Hallucinogen Research: Guidelines for Safety,” Jour. Psychopharm. 22:603-620 (2008). In the most recent and comprehensive review of the scientific literature, the authors actually make the interesting (and perhaps bold) claim that “The incidence of psychotic reactions, suicide attempts, and suicides during treatment with LSD […] appears comparable to the rate of complications during conventional psychotherapy.” See Torsten Passie et al., “The Pharmacology of Lysergic Acid Diethylamide: A Review,” CNS Neuroscience & Therapeutics 14:295-314 (2008).

16 B. Vastag, “Poised to Challenge Need for Sleep, ‘Wakefulness Enhancer’ Rouses Concerns,” Jour. Amer. Medic. Assoc. 291(2):167 (2004).

17 See Judy Illes, Neuroethics: Defining the Issues in Theory, Practice, and Policy (New York: Oxford University Press, 2005); and P. R. Wolpe et al., “Emerging Neurotechnologies for Lie-Detection: Promises and Perils,” Amer. Jour. Bioethics 5(2):39-49 (2005); or T. Metzinger, “Exposing Lies,” Scientific American MIND, October/November:32-37 (2006).

18 Haim Harari, “Democracy May Be on Its Way Out” (2006),