For a long time I regarded neuroscience as a fascinating source of information about the workings of the visual system and its dual pathways for sight and action; the fear system in humans and animals, and numerous puzzling pathology cases arising from site-specific lesions.
Yet, despite the interest of these findings, I had little faith that the profusion of fMRI studies of different cortical regions would tell us much about the problems that had pre-occupied philosophers for centuries. After all, some of the greatest minds of history had long pondered the nature of consciousness, the self, the relation between self and others, only to produce a greater realisation of how hard it was to say something illuminating about any of these phenomena. The more one is immersed in neural mechanisms the less one seems to be talking about consciousness, and the more attends to the qualities of conscious experience the less easy it is to connect with the mechanism of the brain. In despair, some philosophers suggested that we must reduce or eliminate the everyday way of speaking about our mental lives to arrive at a science of mind. There appeared to be a growing gulf between how things appeared to us and how reductionist neuroscience told us they were.
However, I have changed my mind about the relevance of neuroscience to philosophers' questions, and vice-versa. Why? Well, firstly because the most interesting findings in cognitive neuroscience are not in the least reductionist. On the contrary, neuroscientists rely on subjects' reports of their experiences in familiar terms to target the states they wish to correlate with increased activity in the cortex. Researchers disrupt specific cortical areas with TMS to discover how subject's experiences or cognitive capacities are altered.
This search for the neural correlates of specific states and abilities has proved far more successful than any reductionist programme; the aim being to explain precisely which neural areas are responsible for sustaining the experiences we typically have as human subjects. And what we are discovering is just how many sub-systems cooperate to maintain a unified and coherent field of conscious experience in us. When any of these systems is damaged what results are bizarre pathologies of mind we find it hard to comprehend. It is here that neuroscientists seek the help of philosophers in analysing the character of normal experience and describing the nature of the altered states. Reciprocally, what philosophers are learning from neuroscience is leading to revisions in cherished philosophical views; mostly for the better. For example, the early stages of sensory processing show considerable cross-modal influence of one sense on another: the nose smells what the eye sees, the tongue tastes what the ear hears, the recognition of voice is enhanced by, and enhances, facial recognition in the fusiform face area; all of which leads us to conclude that the five senses are not nearly as separate as common sense, and most philosophers, have always assumed.
Similar break-throughs in understanding how our sense of self depends on the somatosensory system are leading to revised philosophical thinking about the nature of self. And while philosophers have wondered how individuals come to know about the minds of others, neuroscience assumes the problem to have been partly solved by the discovery of the mirror neuron system which suggests an elementary, almost bodily, level of intersubjective connection between individuals from which the more sophisticated notions of self and other may develop. We don't start, like Descartes, with the self and bridge to our knowledge of other minds. We start instead with primitive social interactions from which the notions of self and other are constructed.
Neuroscientists present us with strange phenomena like patients with lesions in the right parietal region who are convinced that their left arm does not belong to them. Some still feel sensations of pain in their hand but do not believe that it their pain that is felt: something philosophers previously believed to be conceptually impossible.
I think the startling conclusion should be just how precarious the typical experience of the normally functioning mind really is. We should not find it strange to come across people who do not believe their hand belongs to them, or that it acts under someone else's command. Instead, we should think how remarkable it is that this assembly of sub-systems that keeps track of our limbs, our volitions, our position in space, and our recognition of others should cooperate to sustain the sense of self and the feeling of a coherent and unified experience of the world so familiar to us that philosophers have believed it to be the most certain things we know. It isn't the pathology cases of cognitive neuropsychology exceptional: it is the normally functioning minds that we should find the most surprising.