Descartes process of identifying what is real started with thinking that a identity must be found in whatever remains identical to itself over time. But if that is true my identity would change every time my body aged. Then Descartes realized that the material body is ever changing, and the immaterial soul remains the same throughout time. When I am a bay to compared to now, I am still the same person inside my soul throughout the rest of my time. The material body can not be what identifies us and the immaterial souls is the source of identity.
