My purpose in this paper is to show that the nature of knowledge is such that it is impossible to formulate a perfect definition of it. This problem appeared in ancient times ; Plato was the first to argue that a definition of knowledge is a logical impossibility.
Knowledge is true belief accompanied by an account (επιστήμη έστιν δόξα αληθής μετά λόγου) is the last formulation which Plato considered in his dialogue Theaetetus (202-210); but he refuted it arguing that it is a fallacy, whatever the meaning of the term account (λόγος) might be. He finishes the dialogue leaving the impression that another discussion might provide either a better or even a perfect definition. As far as we know no such solution can be found in any of Plato' s later dialogues ; and the dialogue Philosopher, which he seems (in Sophist) promising to write, was never written; it was not written, in my opinion, because it was not possible to be written.
Later philosophers tried to solve or overcome the logical Gordian knot, but their efforts did not lead to a better result. Any definition, as it seems to me, entails a limitation of our cognitive activity; it is a static expression of what is known (or what seems to be known), although know¬ledge is a ceaseless and restless activity dynamic in character; its «rythm» is dialectical. Therefore, a definition of knowledge is logically impossible as contradictory; it leads to a fallacious circle or a regressus ad infinitum. On the other hand any definition without the predication of truth and certainty could easily be proved insufficient. Thus, I think, it is preferable to say that we cannot define knowledge than provide a mutilated definition. In the final analysis philosophising does not mean solving a problem but making acquaintance with it.
A possibility remains; to search for a definition of knowledge without implying the presupposition of the stability of the object. Probably we shall have to review our philosophy of knowledge. Possibly we shall have to follow the evolution of the conception of knowledge in modern and contemporary science, in order to reach a heraclitean definition of knowledge, since its object is a heraclitean world too.
