WHAT is it like to be a bat? This is the question asked by philosopher Thomas Nagel in his famous 1974 paper. As he explains, if there is something it is like to be the bat – something for the bat – then the bat is conscious. That is what we mean by consciousness. Ask ‘what is it like to be a stone?’ and most people will reply ‘nothing’. Ask ‘what is it like to be my best friend?’ and most people will have a good guess – we believe there is something it is like to be another person. The interesting problems start when we ask about babies, computers or other species. This is why Nagel chose the bat, with its complex world of reflected sounds. The bat’s world must be very different from ours; but surely it has subjective experiences, doesn’t it? This is the question.