Continuing Commentary Commentary on Ned Block (1995). On a confusion about a function of consciousness. BBS 18:227±287. Abstract of the original article: Consciousness is a mongrel concept: there are a number of very different ªconsciousnesses.º Phenomenal consciousness is experience; the phenomenally conscious aspect of a state is what it is like to be in that state. The mark of access-consciousness, by contrast, is availability for use in reasoning and rationally guiding speech and action. These concepts are often partly or totally conflated, with bad results. This target article uses as an example a form of reasoning about a function of ªconsciousnessº based on the phenomenon of blindsight. Some information about stimuli in the blind field is represented in the brains of blindsight patients, as shown by their correct ªguesses.º They cannot harness this information in the service of action, however, and this is said to show that a function of phenomenal consciousness is somehow to enable information represented in the brain to guide action. But stimuli in the blind field are both access-unconscious and phenomenally unconscious. The fallacy is: an obvious function of the machinery of access-consciousness is illicitly transferred to phenomenal consciousness. An example of access-consciousness was criticized by Kinsbourne (1995). Using a distinction similar to without phenomenal consciousness? that proposed by Block, but in a more anatomico-physiologic context, Kinsbourne argues that the ILN can be ªattention-action Joseph E. Bogen coordinatorsº without also being ªsubjectivity pumpsº (p. 168). At Department of Neurological Surgery, University of Southern California, Los one point he suggests that without coordination of attention and Angeles, CA 90033-4620. action ªconsciousness would lapseº; that is, there would be no P without A. His main emphasis is on the possibility that A is Abstract: Both Block and the commentators who accepted his P versus A provided by a different neural basis than P, in which case there distinction readily recognize examples of P without A but not vice versa. As would be the possibility of A without P. Kinsbourne does not, an example of A without P, Block hypothesized a ªzombie,º computa- however, provide examples of A without P. At this point it seems tionally like a human but without subjectivity. This would appear to that we are left with a problem: Are there actual cases of A without describe the disconnected right hemisphere of the split-brain subject, unless one alternatively opts for two parallel mechanisms for P? P? As Block (1995r) put it (p. 277), ªThe relative ease of finding cases of P without A as compared with A without P suggests the Block (1995a) makes a clear conceptual distinction between what distinction is on to something to do with the joints of nature.º He he calls phenomenal consciousness (P) and what he calls access added, ªIf brain damage does not yield cases of A without P, this is consciousness (A). The former (P) he points to by saying that an especially interesting fact given the fantastic wealth of variation ªP-conscious states are experientialº; he gives examples such as in brain-damage cases.º smells, tastes, pains, thoughts, and desires (p. 230). The latter (A) Speaking of brain-damage cases, I would ask, what about split- he describes as a state in which some content is ªpoised for use as a brain humans, with whom I have had a lengthy acquaintance premise in reasoningº and ªpoised for rational control of actionº (Bogen 1993; Bogen & Vogel 1962)? So far as I am aware, no one (p. 231). A can also be ªpoised for rational control of speech,º but has ever denied that: (1) in most of these patients speech is for Block this is not a necessary aspect because he considers produced only by the left hemisphere, (2) the speech is evidence chimps to have A. Indeed, he elsewhere notes that ªvery much that P and A coexist in that hemisphere, and (3) verbal denial of lower animals are A-consciousº (p. 238). information that has been delivered only to the right hemisphere Block is at some pains to consider the possibilities of P without A (and rationally acted upon) reflects the existence of an indepen- and of A without P; in particular, he says, ªIt certainly seems dent capacity in the right hemisphere, that is, an A-consciousness conceptually possible that the neural bases of P-consciousness different from the A-consciousness of the left hemisphere. Does systems and A-consciousness systems are distinctº (p. 233). Block the right hemisphere in that circumstance also possess its own provides some possible examples of P without A (on p. 234 and P-consciousness? (In my scheme, this P is provided by the ILN of p. 244) such as ªbecoming consciousº (acquiring A) of an ongoing the right hemisphere.) Most of us with a personal experience with noise (e.g., a pneumatic drill) some considerable time after one split-brain patients (e.g., Sperry 1974; Zaidel 1978; Zaidel et al. has been ªaware ofº or has been ªexperiencingº it. Although Block 1996) believe that the disconnected right hemisphere also has its is reluctant to accept dreaming as an example of P without A own P-consciousness. The same conclusion has been recently (p. 275), some of us are inclined to agree with Revonsuo (1995) suggested by others (Berlucchi et al. 1995; Corballis 1995). If we that dreaming can be a good example of subjective experience in are wrong, and the right hemisphere of a split-brain patient does the absence of both current perceptual input and behavioral not have a separate P in spite of having a distinctly different A, then output (see also Delacour 1995; ParÂe & LlinÂas 1995). perhaps we have here a readily replicable example of A-conscious- Block suggests a few hypothetical examples of A without P, such ness without P-consciousness. as a ªzombieº that is computationally identical to a person but without any subjectivity. He concludes ªI don't know whether there are any actual cases of A-consciousness without P-conscious- Consciousness by the lights of logic ness, but I hope I have illustrated their conceptual possibilityº and commonsense (p. 233). If there can be A without P as well as P without A, we should Selmer Bringsjord probably conclude that they have distinct neural bases. However, Department of Philosophy, Psychology and Cognitive Science, Department if there can be P without A but there cannot be A without P (that is, of Computer Science, Rensselaer Polytechnic Institute, Troy, NY 12180. A entails P), then there could be one neural mechanism which in selmer6rpi.edu; www.rpi.edu/,brings the case of P without A is temporarily disconnected either from action or from ideation or both. Abstract: I urge return by the lights of logic and commonsense to a dia- lectical tabula rasa ± according to which: (1) consciousness, in the ordinary In my recent proposal (Bogen 1995a; 1995b) that the intra- pre-analytic sense of the term, is identified with P-consciousness, and laminar nuclei (ILN) of a thalamus provide a cerebral hemisphere ªA-consciousnessº is supplanted by suitably configured terms from its Block- with both subjectivity and access to action and/or thought, it was ian definition; (2) the supposedly fallacious Searlean argument for the view explicitly assumed that a single mechanism provides both P and A that a function of P-consciousness is to allow flexible and creative cognition as well as providing, on some occasions, only P. This assumption is enthymematic and, when charitably specified, quite formidable. 144 BEHAVIORAL AND BRAIN SCIENCES (1997) 20:1 Continuing Commentary Block's (1995t) paper, according to Warren (1995), ªadds its own confusion to [the] difficult and dismal topic [of consciousness] (39) When you add together, for each professor (and there are n (p. 270).º Warren proceeds to claim that the terms at the heart of of them), the number of sportcoats owned, and then divide the consciousness dialectic are obscure and to prescribe, there- by n, the result is 5. fore, that the topic should simply no longer be an object of scientific scrutiny. While Warren's view is easily refuted (if the Is there really, out there in the world, this thing Block calls view were correct, then given the obscurity of ªproofº that reigned ªA-consciousnessº? I don't think so. In fact, all his talk of this vaporous concept is easily translated away in the manner of (3) to from Euclid to Frege, following Warren's prescription would have 9 eventuated in a world without classical mathematics!), his attitude, (3 ). Consider, for example, Block's assertion (p. 275) about I submit, is seductive ± because, let's face it, the commentary to prosopagnosia: this point certainly at least appears to be a dark cacophony, with (4) A prosopagnosiac ªlacks A-consciousness of the information consensus, or even near-consensus, nowhere to be sensed, let about the identity of the person.º alone seen. The antidote to Warren's despair is to return by the lights of logic and commonsense to a dialectical tabula rasa ± Sentence (4), courtesy of the definition of A-consciousness Block according to which: (1) consciousness, in the ordinary preanalytic provides, is elliptical for something like sense of the term, is identified with P-consciousness, and ªA- (49) A prosopagnosiac is afflicted by certain failures in the consciousnessº is supplanted by suitably configured terms from its processing of information involved in representing and Blockian definition; (2) the supposedly fallacious Searlean argu- reasoning about faces. ment for the view that a function of P-consciousness is to allow flexible and creative cognition is enthymematic and, when charita- Who needs A-consciousness? Without it, and with some scientific bly specified, quite formidable.