Locke was reacting to the Aristotelian worldview that endorsed the materialistic worldview. For Aristotle, there was only "stuff" but Locke is saying there is more. Aristotle's position seems to boil down to materialism, but not so the position of Locke.
As stated above, Locke had a preference for the dualistic worldview.
Locke thinks that bodies are mysterious and regarding the issue of personal identity he presented done of the most original parts of the Essay Concerning Human Understanding. He agreed with Descartes that one know one is a thinking think but he was not sure of what kind of thing one is.
The identity of a person according to Locke is determined in life by the identity of the soul and this soul in Locke's thought goes on into the afterlife and there must be continuity of identity from this life to the next.
Interestingly, Locke started from a different consideration than most. He argued that immortality has to be personal immortality due to the issues of reward and punishment. He contended that unless the individual who is punished in the afterlife, or rewarded for that matter, then punishment and reward loses its significance.
Locke argued that if we grant the immortality of the soul and that the soul receives reward or punishment in the afterlife, but the individual who receives the reward or the punishment in the afterlife cannot recall what happens on earth then immortality is beside the point. What matters therefore is the consciousness of the individual, the continuity of the consciousness of the individual in the afterlife.
In short, according to Locke's conclusion it is important that I am aware that I am being punished for what I have done. Otherwise what is the purpose or reward or punishment?
