Plato and Aristotle

1. Everybody naturally desires a happy life. But a happy human life is one determined by right choices. So, since whatever enables us to make the right choices in our life is called a virtue, to live a happy life we need to acquire virtues. Furthermore, happiness is the perfection of the totality of a human life. But the only things belonging to the perfection of a human life that do not depend on external circumstances are the permanent good features of the character of a human person. And since such features of character are the virtues, happiness is impossible without acquiring virtues. So, again, in order to live a happy life we need to acquire virtues. But if any mental habits that we acquire in this life we acquire by learning, and virtues are mental habits, then we should acquire virtues by learning, that is, by being taught.
2. But is virtue teachable? In order to answer this question, we need to know what virtue is. But since a question of this type cannot be answered just by looking at the thing, since the thing we talk about is invisible, we can know the answer to such a question only if we can know something a priori, i.e., not based on actual sense experience. But can we know anything a priori? Apparently, as mathematical knowledge indicates, we can. But if so, how is this possible?
3. Plato’s answer is his theory of recollection, coupled with his theory of ideas and his theory of the purely spiritual nature of the human soul. (For further details see the Meno outline, and the Yale Lecture on the Phaedo.)
4. But the theory of ideas in its naïve form, according to which an idea is a universal entity having all and only the common properties of all its particulars, is provably inconsistent. (For further details see Isagoge in your course packet, and the handout Parmenides.)
5. Aristotle, however, manages to avoid this contradiction by deriving our purely intellectual, universal concepts not from a direct intuition of universal entities as Plato’s theory does, but from sense experience by abstraction, the process of separating in thought the universal (common) features (forms) of individuals from their individuat ing conditions, without which, however, they could not exist in reality. (See the underlined passages in the selection from Aristotle’s On the Soul in your course packet, and the handout on Universals.)
6. This will also enable him to work out a rather different theory of the nature of the human soul: the soul does not exist before the body, but, since it is the principle of life, which is the substantial act of being of a living thing, it comes to be with the body, as its substantial form. Still, since universal forms qua universals cannot be received in matter, which is the principle of individuation, the intellective soul, which receives universal concepts, has to be immaterial also according to Aristotle. But the immateriality of the intellective soul for Aristotle need not imply that the soul has its own independent existence, distinct from the existence of the body, as Plato would have it. Rather, the soul and the body are one also in their existence. Still, the soul has this existence so that it is not dependent on the body to continue in this existence, even when it leaves the body, i.e., when the body dies.
7. The immateriality of the soul according to Aristotle can be seen not only from its ability to receive universal forms, but also from its ability to produce them, which is nothing but to immaterialize material forms in the process of abstraction. The faculty of the soul that is able to receive universal forms is called by Aristotle the potential intellect. The faculty that is able to immaterialize material forms in the process of abstraction is called the agent intellect. In fact, the reason why Aristotle has to posit an agent intellect is precisely to account for the soul’s ability to immaterialize the material forms which otherwise can only exist individualized in matter.
8. In this way, Aristotle is also able to account for our having a priori knowledge without the assumption of a preexisting soul. For we know a priori those propositions which we know to be true on the basis of understanding them alone. But this understanding is secured by having the concepts that make up the corresponding thought or judgment in the mind. So, if the concepts are acquired in this life from experience by abstraction, then we certainly need not assume the preexistence of the soul in order to account for a priori knowledge. (For more details on how we acquire the understanding of the first principles of demonstration by induction, see the selection from the Posterior Analytics in your course packet.)