The “Parmenides” of Plato belongs to a stage of philosophy which has passed away. At first we read it with a purely antiquarian or historical interest; and with difficulty throw ourselves back into a state of the human mind in which Unity and Being occupied the attention of philosophers. We admire the precision of the language, in which, as in some curious puzzle, each word is exactly fitted into every other, and long trains of argument are carried out with a sort of geometrical accuracy. We doubt whether any abstract notion could stand the searching cross-examination of Parmenides; and may at last perhaps arrive at the conclusion that Plato has been using an imaginary method to work out an unmeaning conclusion. But the truth is, that he is carrying on a process which is not either useless or unnecessary in any age of philosophy. We fail to understand him, because we do not realize that the questions which he is discussing could have had any value or importance. We suppose them to be like the speculations of some of the Schoolmen, which end in nothing. But in truth he is trying to get rid of the stumbling-blocks of thought which beset his contemporaries. Seeing that the Megarians and Cynics were making knowledge impossible, he takes their “catchwords” and analyzes them from every conceivable point of view. He is criticizing the simplest and most general of our ideas, in which, as they are the most comprehensive, the danger of error is the most serious; for, if they remain unexamined, as in a mathematical demonstration, all that flows from them is affected, and the error pervades knowledge far and wide. In the beginning of philosophy this correction of human ideas was even more necessary than in our own times, because they were more bound up with words; and words when once presented to the mind exercised a greater power over thought. There is a natural realism which says, “Can there be a word devoid of meaning, or an idea which is an idea of nothing?” In modern times mankind have often given too great importance to a word or idea. The philosophy of the ancients was still more in slavery to them, because they had not the experience of error, which would have placed them above the illusion.
The method of the “Parmenides” may be compared with the process of purgation, which Bacon sought to introduce into philosophy. Plato is warning us against two sorts of “Idols of the Den”: first, his own Ideas, which he himself having created is unable to connect in any way with the external world; secondly, against two idols in particular, “Unity” and “Being,” which had grown up in the pre-Socratic philosophy, and were still standing in the way of all progress and development of thought. He does not say with Bacon, “Let us make truth by experiment,” or “From these vague and inexact notions let us turn to facts.” The time has not yet arrived for a purely inductive philosophy. The instruments of thought must first be forged, that they may be used hereafter by modern inquirers. How, while mankind were disputing about universals, could they classify phenomena? How could they investigate causes, when they had not as yet learned to distinguish between a cause and an end? How could they make any progress in the sciences without first arranging them? These are the deficiencies which Plato is seeking to supply in an age when knowledge was a shadow of a name only. In the earlier dialogues the Socratic conception of universals is illustrated by his genius; in the “Phaedrus” the nature of division is explained; in the Republic the law of contradiction and the unity of knowledge are asserted; in the later dialogues he is constantly engaged both with the theory and practice of classification. These were the “new weapons,” as he terms them in the “Philebus,” which he was preparing for the use of some who, in after ages, would be found ready enough to disown their obligations to the great master, or rather, perhaps, would be incapable of understanding them.
Numberless fallacies, as we are often truly told, have originated in a confusion of the “copula,” and the “verb of existence.” Would not the distinction which Plato by the mouth of Parmenides makes between “One is one” and “One has being” have saved us from this and many similar confusions? We see again that a long period in the history of philosophy was a barren tract, not uncultivated, but unfruitful, because there was no inquiry into the relation of language and thought, and the metaphysical imagination was incapable of supplying the missing link between words and things. The famous dispute between Nominalists and Realists would never have been heard of, if, instead of transferring the Platonic Ideas into a crude Latin phraseology, the spirit of Plato had been truly understood and appreciated. Upon the term substance at least two celebrated theological controversies appear to hinge, which would not have existed, or at least not in their present form, if we had “interrogated” the word
