Noûs is that aspect of the soul that grasps theoretical truth and theoretical connections. (I intend a contrast between the theoretical and the practical, between theory and practice.) Theory aspires to be fully explicit knowledge, the best model of which is perhaps plane geometry. A proof in plane geometry, starting from self-evident axioms and moving via patently reliable rules of inference to a theorem, is ideally understood when the proof is comprehended as a whole—when, that is, the nature of the geometrical figure indicated in the proof is brought to lucid contemplation and grasped in an entire vision, as it were, as if before the eye of the mind. Borrowing a phrase from a later philosopher, we can say that noûs aims to achieve “clear and distinct ideas.”
This idea of noûs as theoretic contemplation was made explicit in Aristotle’s conception of God. Let me remark briefly on this conception to indicate further the nature of noetic thought, for Aristotle’s conception of God represents a pure, limiting case of noûs.
Aristotle made a distinction, now deeply embedded in our vision of the world, between actuality and potentiality. In the processes of nature, Aristotle argued, everything tends to become actually what it is potentially. Potentialities are blueprints, as it were, that natural processes tend to follow. Aristotle thought that all natural things, which exist in time and are subject to change, are mixtures of actuality and potentiality. With this distinction in mind, then, it can be said that God, according to Aristotle, is pure actuality. As such, He stands outside or at the limit of nature and so is not subject to time or change.
What sort of actuality is God? Aristotle figured that God must be actuality of the highest, most worthy kind. What kind is highest? Since, Aristotle reasoned, the human being is the highest in nature, the potential that distinguishes the human from the rest of nature must be the highest and its fulfillment the highest activity. There is much that humanity shares with the beasts of nature, but it is a certain sort of reason that distinguishes the human animal from the others. There are several sorts of reason. We reason to figure out, for example, where best to wade a stream, but this instrumental, means-to-an-end sort of reason does not distinguish the highest human potential so much as the sort of reason involved in, say, grasping an elegant mathematical proof. We may call this latter kind of reason contemplative reason.[1] A beast may strategize about crossing a stream, but contemplative reason is unique to human beings.
Thus, Aristotle concluded, the highest activity is that of contemplative reason. Thus, God’s exclusive activity is contemplation. But what does God contemplate? Since the most worthy object of contemplation is God Himself, Aristotle concluded that God’s contemplation is self-contemplation. Further, unlike human contemplation, which struggles to bring its object to view and thus exhibits a mix of potentiality and actuality, God’s contemplation is absolutely complete, leaving nothing of its object from its vision. Thus, God, on Aristotle’s conception, represents the goal of complete self-understanding, holding within transparent noetic contemplation a completed knowledge of Himself (and therefore, by virtue of a universal kinship, of all there is to know). Aristotle’s God, you might say, is the end of philosophy.
[1] The activity of contemplative reason is called theoria. Thus, another English phrase adequate to the purpose is theoretical understanding. Theoria, on Aristotle’s vision, is what human beings share, in a limited way, with the divine, and is also what makes them distinctly human. Thus, the essential, distinctive activity of a human being is to understand. A horse, given the right environment, will simply live out its life, fulfilling its potential, without ever understanding what sort of being it is. Humans, though, can inquire and theorize and so understand what sort of beings horses are. Remarkably, they can also understand what sort of beings they themselves are. This latter turns out to be a much more delicate enterprise, but Aristotle considered such self-understanding to be necessary for a fully human life. In a famous passage, Aristotle stated that humans desire by nature to understand. See Aristotle’s De Anima, “On the Soul.”