EN
The aim of the article is to show how the Aristotelian contents “potentiality” and “potency” have been mixed up in the Arabic legacy, especially in Avicennian philosophy. Whereas Aristotle distinguished between potentiality as the logical term and potency as the ontological one, Avicenna combined them and concluded that potentiality can be regarded as the concerning the level of real being. This confusion has been held later by, for example, John Duns Scotus. It was great service of Thomas Aquinas, who discerned two concepts and precisely indicated that they belong to the different and irreducible orders: logical and ontological one.