This study deals with the psychological, metaphysical and scientific ideas of two major and influential Aristotelian philosophers of the Italian Renaissance - Nicoletto Vernia (d.1499) and Agostino Nifo (ca. 1470-1538) - whose careers must be seen as interrelated. Both began by holding Averroes to be the true interpreter of Aristotle"s thought, but were influenced by the work of humanists, such as Ermalao Barbaro, though to a different degree. Translations of the Greek commentators on Aristotle (Alexander of Aphrodisias, Themistius and Simplicius) provided them with new material and new ways of understanding Aristotle - Nifo even put himself to learning Greek - and led them to abandon Averroes, especially as regards his views on the soul and intellect. Nevertheless, both Vernia and Nifo engaged seriously with the thought of medieval scholars such as Albert the Great, Thomas Aquinas and John of Jandun. Both also showed interest in their celebrated contemporary, Marsilio Ficino.