Central to Aristotle’s metaphysics is the question of individuality. The individuality of each substance is explained in relation to “matter” because the “form” is universal. Avicenna, as one of the Aristotelian Neoplatonist philosophers, is not content with this explanation and proposes to establish individuality on other grounds. In this paper, I argue that in his perspective it is not the “matter” which determines individuality but rather the principle of existence.