Abstract

This dissertation attempts to demonstrate that the Platonic thesis that thought is like a dialogue of the soul with itself, in the form it is given in the philosophy of Wilfrid Sellars, is a key to the metaphysics of transcendental subjectivity, and can be used fruitfully as a foil in critically interpreting the classical Cartesian and Kantian texts on the metaphysics of the subject. The metaphor becomes fruitful only when developed in the direction of a functional account of acts of thought, according to which the concepts of intentionality are indifferent as to the material constitution of the items which function in such a manner as to be acts of thought. ;Chapter I demonstrates that although the Platonic thesis appears again and again in ancient and Medieval texts, a functional account is never pursued seriously. The tradition assumes that acts of thought are "diaphanous." Chapter II shows that although there are hints of a functional turn in Descartes' distinction between ideas materialiter and ideas objective, he remains true to the tradition in developing his substance metaphysics of the subject. After a brief look at Leibniz in Chapter III, Chapter IV shows how Kant makes the turn to a functional account of the thinking subject, according to which it is a category mistake to say that the transcendental 'I' is in the world either phenomenally or noumenally. Chapter V shows how Wilfrid Sellars develops the Kantian position by taking up the Platonic thesis and interpreting it in a functional direction. This opens up the way to a positive metaphysics of transcendental subjectivity which is able to do justice to the fact that the subject which constitutes the world is also a subject in the world