||In his On the Soul, Aristotle offers one of the first systematic accounts of the soul and of its role in explaining living activities. In book one he criticizes the views of his predecessors, Plato and the Pre-Socratics. In books two and three, Aristotle develops his own account of the soul, characterizing it as the fulfillment or actuality of an organic body. The soul is the principle that makes the bodies of living things actually be alive. Thus, on his account, living things are composites of matter and form: they are hylomorphic (the technical term for Aristotle's view, based on the Greek words for matter and form). After laying out this general account, Aristotle discusses three fundamentally different kinds of soul power: a nutritive or vegetative power that allows living things to grow, nourish themselves and reproduce; a perceptual power that allows animals to perceive and respond to the world around them; and an intellectual power that allows human beings to understand the natures of things. Aristotle characterizes the powers these souls have by analyzing their activities and the objects these activities involve (e.g. in order to define the power of perception, he gives an account of the activity of perception and an account of perceptible objects). Aristotle's text was the key reference point for much of ancient and medieval psychology and philosophy of mind and has continued to have a significant influence up to the present day. There has been continuing debate on the extent to which Aristotle's hylomorphism represents a distinct or viable position when seen from the vantage point of contemporary philosophy of mind (see Aristotle:Soul for further details). Both the overall orientation of Aristotle's philosophy of mind (e.g. is it naturalistic or not?) and the details are highly controversial, as the articles in this category and its subcategories make clear.