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The Phaedo

Against Strong Concept Empiricism

  1. Suppose that all of our concepts are derived from sensory experience; specifically, suppose that we acquire the concept C by identifying similarities among diverse experiences of instances of C and generalizing on the relevant feature common to all of them (viz., C-ness). [Premise – cf. 74c]
  2. One of our concepts is similarity. [Premise]
  3. So if (1) is true, we acquire the concept of similarity by identifying similarities among cases of similarity and generalizing on the relevant feature common to all of them (viz., similarity). [1, 2]
  4. But (3) is absurd: the acquisition of a particular concept can’t presuppose possession of that very concept. [Premise]
  5. Therefore, (1) is false: some of our concepts are not so acquired. [1, 4]

The Argument from Imperfection

  1. Whenever we judge that some perceptible object is equal (to another), larger, smaller, beautiful, good, just, pious, etc., we judge that it is only imperfectly so. [Premise]
  2. If one judges that a perceptible object is only imperfectly F, she must have in mind something that is perfectly F to which she compares it and recognizes it to fall short of in terms of F-ness. [Premise]
  3. So we often have in mind something that is perfectly F. [1, 2]
  4. So there is something such that it is perfectly F and we have it in mind [3]
  5. So there is something that is perfectly F. [4]
  6. But no perceptible object is perfectly F. [Premise]
  7. Hence, there is something that is perfectly F (call it the “Form of F-ness”), distinct from any perceptible object, in comparison to which we judge perceptible objects to be imperfectly F. [5, 6]

[Corollary: Since we cannot have come to have the Form of F-ness in mind by experiencing any perceptible object (see (6)), we must have it in mind due to experiencing the Form itself in some prenatal state of existence.]