Philosophy of mind used to be a largely speculative business, or at any rate, its only empirical basis was in the phenomenological scrutiny of the effects of mind itself. Modern neuroscience is changing that situation. V.S. Ramachandran and S. Blakeslee, Phantoms in the Brain, Harper Perennial, 2005 is an account of the impact the study of the brain is having on traditional questions "about the nature of the self: Why do you endure as one person through space and time, and what brings about the seamless unity of subjective experience? What does it mean to make a choice or to will an action?". He describes his own work as "experimental epistemology" (p. 3); the best I can do here is to pull out some of the more striking points that emerge.

One is the embodied nature of the self; but it is not merely that the self is embodied, it is that the limits of the body are not absolute. The body is so much in and of the world that there is no absolute division between it and its surroundings, as VSR shows by some readily performable experiments (p. 59). This chimes very neatly with the philosophical account of being-in-the-world given by Heidegger, but also with such mundane experiences as playing racquet sports, or a musical instrument, or wielding a weapon of some kind; after some practice, one's feeling literally goes into the object so that it becomes an extension of oneself.

Also striking is the divorce between the intellectual and the sensible functions of the brain; patients with right-brain injuries due to strokes can end up neglecting the half of the world that is on their left hand side, but remain capable of conversations about abstract intellectual subjects including politics or chess (p. 126). It is as if their perceptions have been altered without their intellectual rationality being remotely impaired.

VSR draws on Kuhn's idea of a 'paradigm shift' to illustrate the idea that different regions of the brain are responsible for constructing different stories about reality. "The left hemisphere's job is to create a belief system or model and to fold new experiences into that belief system. If confronted with some new information that doesn't fit the model, it relies on Freudian defense mechanisms to deny, repress, or confabulate - anything to preserve the status quo. The right hemisphere's strategy...is to play "Devil's Advocate," to question the status quo and to look for global inconsistencies. When the anomalous information reaches a certain level...The right hemisphere thus forces a "Kuhnian paradigm shift"' (p. 136)

VSR emphasizes "an important principles about brain function [is] that all our perceptions - indeed, maybe all aspects of our minds - are governed by comparisons and not by absolute values...true whether you are talking about something as obvious as judging the brightness of print in a newspaper or something as subtle as detecting a blip in your internal emotional landscape" (p. 167). This extends to our sense of our own self, and the selves of others - as when patients suffer from the delusion that their loved ones are impostors, or that a photograph of themselves is really of a double. Interestingly, the roots of this disorder appear to stem from injury to a part of the brain concerned with emotion, suggesting that there is no such thing in ordinary experience as a perception or sensation that is free from value.

The upshot is that there is no absolute barrier between mind and brain, something that bears on the problem of qualia, or the private subjective character of perception. VSR writes "the problem of qualia is not necessarily a scientific problem...your scientific description is complete. It's just that your account is incomplete epistemologically because the actual experience of electric fields [for a fish] or redness [for a colourblind person] is something you will never know...there is no such barrier, no great vertical divide in nature between mind and matter, substance and spirit...this barrier is only apparent and...it arises as a result of language. This sort of obstacle emerges when there is any translation from one language to another" (p. 231)

VSR does not mention any of the other philosophers who have written on the nature of translation, but what he has to say seems at least relevant to the kinds of debates that someone like Donald Davidson was involved in. VRS argues that "we are dealing here with two mutually unintelligible languages. One is the language of nerve impulses - the spatial and temporal patterns of neuronal activity that allow us to see red, for example. The second language, the one that allows us to communicate what we are seeing to others, is a natural spoken tongue like English...Both are languages in the strict technical sense, that is, they are information-rich messages that are intended to convey meaning, across synapses between different brain parts in one case and across the air between two people in another" (p. 231).

One might object that in fact the idea of neuronal activity as a language rests ultimately on an analogy with natural language that breaks down if we push it too hard; it is difficult to see electrical impulses of any kind, including those that occur in the brain, as being intended to convey meaning. Nevertheless, if what VSR is saying is that what is occurring in the brain has its analogue in what is occurring in the mind, but that this is not a causal relationship even though the former is the condition of the latter, it seems hard to object.

VSR's work has also allowed him to suggest three conditions for consciousness which allow him to separate human consciousness off from that found in other creatures. These are (i) the possession of irrevocable qualia - I cannot merely choose what to perceive in the world in the same way that I can choose what to picture to myself in imagination (ii) the possibility of flexibility in response to these qualia - on seeing the guard dog, I can back away or stand my ground or climb a tree and (iii) possession of a short-term memory which ensures the stability of the world of qualia. Where any one of these is absent, there is no consciousness in the human sense. (pp. 238-40)

So, the bee that returns to the hive and does an elaborate dance to indicate where the pollen it has discovered is to be found is not conscious, because it has (i) and (iii) but not (ii); the dance it performs is not an instance of a flexible response, it is a pre-programmed pattern. In the same way, a sleepwalking person is not conscious, in the sense that we ordinarily use the term, because in this case (iii) is absent; sleepwalkers typically have no memory of their actions although they are clearly responding to their environment at some level.

VSR concludes that the self is at once embodied, passionate, executive, mnemonic, unified, vigilant, conceptual, and social (pp. 247-53); it is "imposing coherence on consciousness" (p. 251). "All of us make mental taxonomies or groupings of events and objects...Our brains set up...categories...even without formal education". We seem to naturally grasp the world according to what "cognitive psychologists and philosophers" call "tokens and types", so that "all our experiences can be classified into general categories or types (people or cars) versus specific exemplars or tokens (Joe or my car)...this distinction is not merely academic; it is embedded deep in the architecture of the brain" (p. 170).

At the same time 'our sense of having a private nonmaterial soul "watching the world" is really an illusion (as has long been emphasized by Eastern mystical traditions like Hinduism and Zen Buddhism)...you are in fact part of the eternal ebb and flow of events'. He is no doubt right to find this liberating and the source of 'a certain humility - the source of all authentic religious experience' (p. 257).