 A modified version of Avicenna’s theory of the giver of forms appears in John Buridan, who deviates from the dominant position that the form of human beings comes from without, i.e. from God, whereas that of animals is educed from matter. In contrast, Buridan holds that all forms are given by a separate incorporeal substance, which he calls God. The phenomenon of spontaneous generation supports this view, since it cannot be explained with the influence of the stars, which is too weak and imperfect to generate animals (In Metaphysicen Aristotelis lib. 8 q. 9). What does not appear in Buridan, is Avicenna’s theory of the subsequent mixtures of elementary qualities.