This study aims to highlight that why and how much the views of Averroes and Thomas Aquinas, who formed their own doctrines of intellect on Aristotle's intellect doctrine, differentiate on the possibility of material intellect conjunction with agent intellect and their identity. Averroes partly adopted the view of Ancient Greek commentators -Alexander of Aphrodisias, Themistius- and Ibn Bajja's agent intellect thesis and he argues that the agent intellect is external, eternal and one, its conjuncts with each individual through intelligible. Nevertheless, Aquinas argued that the agent intellect is united to the soul as its faculty and it numerically multiplied according to the number of individuals. Aquinas, who agrees with Averroes for the abstraction and actualization of intelligible, has criticized Averroes' separate and one agent intellect doctrine from two points: The first one is that the agent intellect is not a separate, single and common intellect, and the second it if separate intellect conjunct with individuals through intelligible it will not suffice to make each individual understand per se. Therefore, in order for the individual to be per se understand, the agent intellect should not be a discrete, transcendent, and a single intellect, but an actual aspect of faculty of the individual intellectual soul.