Richard Swinburne on Animal Souls

At which stage of the evolutionary process did animals first start to have souls and so a mental life? We do not know. But fairly clearly their behaviour shows that the mammals do have a mental life. My view is that all the vertebrates have a mental life, because they all have a brain similar to the human brain, which, we know, causes a mental life in us, and their behaviour, too, is best explained in terms of their having feelings and beliefs. Dogs and birds and fish all feel pain. But there is no reason at all to attribute a mental life to viruses and bacteria, nor in my view to ants and beetles. They do not have the kind of brain which we do, nor do we need to attribute feelings and beliefs to them in order to explain their behaviour. It follows that at some one particular moment in evolutionary history there appeared something utterly new—consciousness, a mental life, to be analysed in terms of souls having mental properties.

The reluctance of so many philosophers and scientists to admit that at a particular moment of evolutionary history there came into existence, connected to animal bodies, souls with mental properties seems to me to be due in part to the fact that, if such a thing happened, they are utterly lost for an explanation of how it came to happen. But it is highly irrational to say that something is not there, just because you cannot explain how it came to be there. We should accept the evident fact; and if we cannot explain it, we must just be humble and acknowledge that we are not omniscient. But I am going on to suggest that, although there cannot be an inanimate explanation, of the kind characteristic of the natural sciences, of the occurrence of souls and their mental life, the theist does have an explanation.

(Richard Swinburne, Is There a God? [Oxford: Oxford University Press, 1996], 79-80)