THE aim of this paper is to explain a paradox in Plato's philosophy. On the one hand, Plato reduces virtue to knowledge; on the other, he rejects the possibility of knowledge or at least has serious doubts that it exists. I shall propose in this paper that the definition of virtue as knowledge is a logical outcome of Plato's denial of the particular aspect of knowledge as cognitive relation. This paper may also be considered as an attempt to resolve the (...) Hintikka‐Santas polemic about whether there is a difference in Plato's philosophy between the function of knowledge and its object. ([3], [6] pp. 1–71). The first part of this paper consists in a critical exposition of Plato's rejection of cognitive relation as a function of knowledge. The second part is devoted to an account of Plato's assumptions in this regard. In the third section of the paper I shall show how, on the basis of these assumptions, Plato reduces virtue to knowledge. And finally, in the last section of the essay, I shall compare my interpretation of this issue with other modern interpretations, especially those of Gerasimos Santas and Jaakko Hintikka. (shrink)