Like many other AI practitioners, I’m a philosophical functionalist: I believe that a cognitive state, such as one derived from reading, should not be defined by what it is made of in terms of hardware or biology, but instead by how it functions, in relation to inputs, outputs and other cognitive states. (Opponents of functionalism include behaviourists – who insist that mental states are nothing other than dispositions to behave in certain ways – and mind-brain identity theorists – who argue that mental states are identical with particular neural states, and are tied to specific biological ‘hardware’.)