The result is a succinct argument for the existence of the soul in human persons. His argument goes like this:
- I am a substance which is thinking.
- It is conceivable (i.e. logically possible) that while I am thinking my body is destroyed.
- It is not conceivable (i.e. not logically possible) that 'I am thinking and I do not exist.'
- I am therefore a substance which, it is conceivable, can continue to exist while my body is destroyed.
- It is not conceivable (i.e. not logically possible) that a substance can lose all its parts simultaneously and yet continue to exist.
- Therefore, I am a soul, a substance, whose only essential property is the capacity for thought.
Therefore, there must be more to my existence than just the existence of my body. There must be something about me that can continue to exist when every part of my body is destroyed.
That other part of me must be, from 1. and 2., that part of me which thinks, i.e. a soul (or mind), and which I identify as myself.
Swinburne gives a cogent defense of this argument in the book, which, though he claims it to be written for a broad audience, would be rather hard going for someone with little background in philosophy.
Nevertheless, in an age in which the reigning view on these matters is a philosophical materialism which denies the existence of a soul or mind, Swinburne's book is refreshing.