Humans are explanation hungry. We want explanations, and at a pinch we will settle for something which has the form of an explanation, even if the purported explanation, upon examination, proves to be a vacuous one. One standard way to proceed when we are in need of an explanation is to suggest a name for whatever it is that is causing the phenomenon or set of phenomena that needs explaining. To do this is to invoke a theoretical entity. Soul is a theoretical entity, and we may wonder why it has remained in circulation for so long, with so little explanatory power or evidential support. Souls have a number of functions, but despite the number of functions, the entity that has those functions is a single entity. In the normal case, identity requires spatio-temporal continuity. The soul is a form, and the human form is one and the same for all humans; nonetheless we do have individual souls.