Some Points of Difference between Plato and Aristotle

Plato (428-348 BC)

There is a priori knowledge (Meno)

1. Intellectual concepts of perfect objects needed for a priori knowledge cannot be gained from experience (main argument of the Phaedo for recollection)

2. A priori knowledge = prenatal knowledge (theory of recollection in Phaedo)

3. The objects of our intellectual concepts (i.e. the things we directly conceive by means of our intellectual concepts) are the perfect Forms.

Aristotle (384-322 BC, Plato’s student: amicus Plato sed magis amica veritas – ‘I like Plato but I like the truth even more’)

There is a priori knowledge.

4. Intellectual concepts needed for a priori knowledge can be gained from experience, by abstraction (On the Soul).

5. A priori knowledge is not prenatal, but can be gained by induction based on abstraction (Posterior Analytics).

6. The objects of our intellectual concepts are the natures (essences, quiddities) of material things (On the Soul); these objects cannot be the perfect Forms of Plato, for such perfect Forms cannot exist (see the handout on “Plato’s Theory of Forms and its problems”, as well as the handout on Plato’s Parmenides; both available in the class folder.)

Is Aristotle a materialist (as a “harmony theorist” would be) or is he an idealist (as is Plato) concerning the nature of the soul? (That is to say: does he believe that the soul is just the organic structure of the body, or does he believe that it is an immaterial, spiritual entity inhabiting the body?)

Reply: he is a materialist concerning non-human souls, but he also contends that the human soul, which has an immaterial activity, namely, thinking, is not dependent for this specific activity, and so neither for its being, on its union with the body; therefore, the human soul (at least its intellective “part”), is immortal.