The Limits of Sentience

Nicholas Humphrey, Cambridge University 

Who or what in the world could be phenomenally conscious, besides ourselves? Some theorists speculate that there is consciousness all the way down, so that all animals and even elementary particles are conscious to at least a small degree. Others, more soberly, suppose that consciousness is linked to complex information processing, and is likely to have emerged wherever there is evidence of sophisticated intelligence, either in animals or machines. I think both views are profoundly mistaken. I believe phenomenal consciousness is an evolved adaptation, involving dedicated brain circuitry, that has been designed by natural selection specifically because of the advantageous changes it produces in an individual's sense of self and outlook on life. This means it can have evolved only in such animals as already had (a) brains suitable to house it, and (b) life-styles suitable to benefit from it. If this is right, sentience must be a relatively late evolutionary development, that is rare among animals, and cannot possibly have arisen among non-living things.