The present work seeks to identify which systems of philosophical metaphysics, if any, are compatible with assumptions about evolutionary gradualism. The thesis is that any advocate of a self-preserving soul must somehow integrate that soul into an organic body that is the product of an evolutionary history. This tension between a present/absent trait (the soul) and an incrementally changing substrate (the body) represents a version of the sorites paradox: at what point in the gradual evolution of Homo sapiens was the step taken from the soul-less to the ensouled? The posture adopted here is that, given a standard of Popperian verisimilitude, any incompatibility between these two systems of thought signals a weakness in the soul-theory, and not in evolution.

Having outlined the problem, the text then evaluates the soul-theories of five influential philosophers: Plato, Aristotle, William of Auvergne, Hume, and Heidegger. Each is evaluated on the same three criteria: First, is the soul-theory internally consistent; second, is the kind of soul depicted in that theory one which the ordinary person would recognize as his or her "self," such that there would be an interest in whether or not it survives physical death; and third, is the soul-theory compatible with evolution under a criterion of psychological continuity across species?

Of the five systems discussed, none successfully surmounts all three criteria. Hume's, however, seems most promising. Had the evolutionary criteria not been included, Heidegger's would have been the better choice, demonstrating that evolutionary considerations do have fundamental philosophical consequences. No final conclusions are offered, of course, because some as yet unanalyzed system of metaphysics might fully satisfy the criteria. The long term contribution to intellectual discourse is therefore the description of a suitable method by which this question can be approached. [M.A. thesis]