Secular philosophy has struggled to give a satisfactory account of personal identity, especially considering developments in science and scenarios in science fiction that have provided material for thought experiments. The rejection of the persistent self has ramifications for ethics. If I am a different person from the man who married Mrs X twenty years ago, am I under any obligation to keep vows that he made? In theological circles, this question has a bearing on the judgement of sin. Is God right to judge the person I am today for sins committed by “someone else” in the past? The unease that this question provokes has caused people of faith to re-engage with the question of selfhood and personal identity.
Modern cellular biology provided grounds for rejecting the view that the body was the source of personal identity. In the wake of this development, it has become necessary to seek less tangible hypotheses to account for personal identity and personal moral agency. The soul is an obvious candidate (in the case of those who believe in its existence). Nevertheless, is the soul a sufficient condition for personal identity? As beings of the physical plane, our sensory experience mediates our conception of reality. It is hard to conceive of existing without referring to concepts derived from physical objects experienced by means of the body. Should we then posit that both the body and the soul are necessary conditions for personal identity?
People of faith, believing in beings such as angels and demons, might respond that these entities are persons: they have will, memory, intellect, and emotions. Nevertheless, physical bodies do not define such entities in the way that they do humans – even if one admits that such entities have the power to assume physical bodies (cf. Gen. 6:1-6). The presupposition that physicality is not necessary for existence provides a foundation for belief in such entities.
The materialist rejects the proposition that spirit-beings exist. He “refutes” evidence of their existence by claims of mistinterpretation, mental and/or physical illness, and deception. Furthermore, he challenges dualist doctrine with the mind-body problem. If the mind and body are completely different kinds of thing, how can one affect or control the other? It is not possible to offer an anology in response to this problem without begging the question. An analogy from the physical world fails at the critical point of comparison, for the two elements have physicality in common. Stating the God moves the world asserts what the materialist requires the believer to prove, namely that non-physical beings exist.