The Principle of Individuation in the Constitution of the Human Person

It is generally considered that the principle of individuation is matter and that this doctrine comes from Aristotle. This paper will examine how medieval philosophers approached this problem and we will show that they offered various theories by which the principle of individuation could be matter, form, combination of matter and form, accidents or some special principle such as haecceitas, which we find in the school of J. Duns Scotus. We will assess how all these theories resolve the problem only partially, and thus indicate the need of a single principle of individuation. This becomes particularly relevant in the context of the metaphysical study of a human person. Our research will show that it is actus essendi, which is not only the act of all acts, but also the principle of all principles.