"Parmenides" 132c-133a and the Development of Plato's Thought
The crucial question in the issue of Plato's philosophical development is whether he ever abandoned or significantly modified the theory of forms. Most pertinent to this question is the nature of Plato's response to his own critique of the theory in the Pannenides. Scholarly opinion on this issue is so divided that it may safely be called the most vexed problem in the interpretation of Plato.
In this paper I shall consider only one view of the force of the Parmenides arguments on Plato's development: that of G. E. L. Owen. According to Owen, one of the arguments of the Parmenides, the so-called second version of the Third Man Argument. conclusively refutes the view of the middle dialogues that the forms are paradigms. After the Parmenides, Owen holds, Plato either adopted the view that the forms are immanent universals or gave no interpretation of their nature. 1 Owen uses this conclusion to support his claim that the Timaeus, in which the forms are construed as paradigms, antedates the Parmenides.
I shall attempt to show that the argument of the Parmenides on which Owen relies does not refute the claim that the forms can be understood as paradigms. even though the argument may be formulated so as to be formally valid. In the absence of other textual evidence that Plato modified the theory of forms, then, it cannot be proved that the paradigm version of the theory is the exclusive property of Plato's middle period, or that the Timaeus is therefore a dialogue of that period.2
Prior, W. J. (1979). “Parmenides” 132c-133a and the Development of Plato’s Thought. Phronesis, 24(3), 230–240.