Celebrated Islamic theologian, controversialist, and polymath. Al-Razi anticipated the objections both Locke and Kant made to philosophies that think of the soul as a different immaterial entity, a persistent guide or driver over and above the doings of the person. He saw that just as when you see the same house, you cannot be sure it has the same owner, so on this theory (later revived by Descartes) the same would be true of seeing the same person or human being.