SUMMARY
Aristotle's cosmology, especially his viewpoint about generation, is deeply rooted in the theory of form and matter. Although Avicenna accepts the Aristotelian theory of form and matter, he makes some alterations in this theory and redefines it in a new manner. His theory of form and matter despite its Aristotelian background is mostly influenced by his own metaphysical bases which are originally inspired by the monotheistic spirit of Islamic teachings. As a result, while in Aristotelian cosmology the prime matter of the world is eternal and uncreated, Avicenna by making a distinction between temporal eternity and essential eternity of the world, rejects the former while accepts the latter. Accordingly, the prime matter is essentially in need of an efficient cause to bring it to existence. Besides, since prime matter as the mere potentiality cannot exist without any actuality or form, necessarily the efficient cause at the same time bestows forms upon it. Consequently, while in Aristotelian viewpoint, forms are emerged in the prime matter due to its eternal motion toward the full actuality, or as he occasionally calls it, unmoved mover, in Avicenna’s philosophy forms are bestowed upon matter by an external cause and the internal motion of matter just plays a preparatory role for its actualization.