Aristotle's teaching on the intellective soul (De anima III.4–5) serves as the starting-point for Renaissance discussions and, therefore, predetermines the questions raised and the answers given. In the Averroist tradition, this was treated as the beginning of the entire third book. Chapter 4 attempts to define the activity of the intellective soul through analogy to sense-perception and by so doing introduces an interdependence between psychological and epistemological theories. In the fifth chapter, distinguishing between the possible and the agent intellect, Aristotle goes beyond the analogy with sense-perception and alludes to the active role of the soul in the process of knowing. This extremely condensed and enigmatic chapter has provoked many different interpretations, ranging from the outright denial of the agent intellect to the postulation of an agent sense as well, in order to maintain the analogy with sense-perception. For those commentators, however, who kept between these two extremes, III.5 provided both the chance and the need for metaphysical speculation on the ontological status of the intellective soul including its relation to the celestial intelligences and the question of its immortality. It was to this last question that particular attention had to be paid, since on the one hand, Aristotle is not explicit about it, and on the other, Christian doctrine required an affirmation. Thus, for the Middle Ages the question was not whether the human soul was immortal but rather how an immortal soul could fit into the ontological structure of the universe. Consequently, the metaphysical point of view gained prominence, until, in fourteenth-century nominalism, metaphysics lost ground and a new approach was possible from the perspectives of natural philosophy and epistemology.