📰 The Unity of Consciousness

Human consciousness usually displays a striking unity. When one experiences a noise and, say, a pain, one is not conscious of the noise and then, separately, of the pain. One is conscious of the noise and pain together, as aspects of a single conscious experience. Since at least the time of Immanuel Kant (1781/7), this phenomenon has been called the unity of consciousness.

When I consider the mind, that is to say, myself inasmuch as I am only a thinking thing, I cannot distinguish in myself any parts, but apprehend myself to be clearly one and entire. [Descartes 1641: 196]

Notice where it is that I cannot distinguish any parts. It is in “myself inasmuch as I am only a thinking thing” (ibid.); that is, in myself as a whole—which requires unified consciousness of myself as a whole. The claim is that this subject, the target of this unified consciousness, is not a composite of parts.

In Kant (1781/7), the notion that consciousness is unified is central to his ‘transcendental deduction of the categories’

Kant claims that in order to tie various objects of experience together into a single unified conscious experience of the world, we must be able to apply certain concepts to the items in question.

It should have followed from his atomism that there is no unified consciousness, just “a bundle of different perceptions” ([1739] 1962: 252). Yet, in a famous appendix, he says that there is something he cannot render consistent with his atomism (p. 636). He never tells us what it is but it may have been that consciousness strongly appears to be more than a bundle of independent ‘perceptions’.

No medical procedure to do with consciousness has received as much philosophical attention in recent times as commissurotomies, more commonly known as brain bisection operations. Nagel (1971) was perhaps the first philosopher to write on them; his paper continues to be influential. Since then, Puccetti (1973, 1981), Marks (1981), Hirsch (1991), Lockwood (1989), Hurley (1998), Bayne (2008, 2010), Schechter (2010) and many, many other philosophers have written on these operations. Indeed, the strange results of these operations in certain controlled conditions was one of the things that brought the unity of consciousness back onto the cognitive research agenda.

In normal life, patients show little effect of the operation. In particular, their consciousness of their world and themselves appears to remain as unified as it was prior to the operation. How this can be has puzzled a lot of people (Hurley 1998). Even more interesting for our purposes, however, is that, under certain laboratory conditions, these patients seem to behave as though two ‘centres of consciousness’ have been created in them. The original unity seems to be gone and two centres of unified consciousness seem to have replaced it, each associated with one of the two cerebral hemispheres.

In some particularly severe forms of schizophrenia, the victim seems to lose the ability to have an integrated, interrelated experience of his or her world and self altogether. The person speaks in ‘word salads’ that never get anywhere, indeed sometimes never become complete sentences. The person is unable to put together perceptions, beliefs and motives into even simple plans of action or act on such plans if formed, even plans to obtain sustenance, tend to bodily needs, escape painful irritants, and so on. Here, it is plausible to suggest that the unity of consciousness has shattered rather than split.

In the history of European philosophy at least since Locke, diachronic unified consciousness has been closely linked to personal identity in the philosopher’s sense, i.e., continuing to be a single Person, one and the same person, across time.

Dennett articulates an even more radical view, on both unity and the architecture of it. For him, unified consciousness of ‘self’ is simply a short-lasting ‘virtual captain’ coming to be as a result of a small group of information-parcels gaining temporary dominance in a struggle with other such groups for control of such cognitive activities as self-monitoring and self-reporting. We take these transient phenomena to be more than they are because each of them is the ‘me’ of the moment and they are tied to earlier transient selves by the special form of autobiographical memory identified earlier. If the temporary coalition of conscious states that is winning at the moment is what I am, is the self, each temporal chunk of ‘self’ is likely to be found in different parts of the brain from other such chunks and there will be many NCCs of unified consciousness in many different places.