In the Sophistes the main discussion is led up to through a defini tion of the "sophist" as an "illusionist," a person who, by abuse of logic, produces the illusion, or false appearance, that nature and human life are alike riddled by insoluble contradictions. (This shows that the persons aimed at under the name "sophist" are the Megarian controversialists who make an illegitimate use of the dia lectic of Zeno and Socrates.) Now the "sophist" himself would retort that this definition is senseless, for there can be no such thing as a false statement or a false impression. For the false means "what is not," and "what is not" is nothing at all, and can neither be uttered nor thought. To refute him we need to correct the fundamental thesis of so venerable a thinker as Parmenides.
We must either admit that there can be no false statements, or we must be prepared to maintain that "what is not, in some sense also is,' and "what is, in some sense is not" (i.e., we must explain what is the meaning of a significant negative proposition). In our theory of "being" we have to meet at once Parmenides and two different types of pluralist opponents of Parmenides, (a) the cor porealists who say that the real, "what is," is just visible and tangi ble body, and (b) certain "friends of Forms" who maintain that the real is a multitude of incorporeal Forms, denying that sense perception gives us any apprehension of it. The corporealist is sufficiently refuted by the consideration that he himself cannot deny the reality of "force" (bbva,uts) and that force is not a body. The incorporealist "friends of Forms" cannot be met in this way. They regard force, or activity itself as belonging to the unreal realm of "becoming." We meet them by urging that knowing is itself an activity and that we cannot deny intelligence and knowl edge to the supreme reality. This means that it has a "soul" and is alive. But if life is real, movement and repose from movement must be real too.' This leaves us free to attack the Parmenidean Monism itself. That is refuted by drawing the distinction between absolute and relative "non-being." A significant denial, A is not B, does not mean that A is nothing, but that A is other than B. Every one of the great categorical features of reality is other than every other, and the true business of "dialectic" is to study the various possible combinations of these universal "categories." The dialogue men tions five of them, being, identity, difference, motion and rest. It is not said that this is a complete list of "categories," though it was treated as such by the Neo-Platonists.
The important result is thus that we have learned to think of Forms themselves as an inter-related system, with relations of compatibility and incompatibility among themselves. Negation is a moment in the system of intelligible reality, and therefore its presence in the sensible realm does not stamp that realm as illu sion. This is the ontological position which interests Plato ; the recognition of the function of the logical copula is a consequence.
The Politicus has as its main result the conclusion that gov ernment by the personal direction of a benevolent "dictator" is not suitable to the conditions of human life, where the direction is necessarily that of a fallible man, not of a god. In an actual human society, the surrogate for personal direction by a god is the impersonal supremacy of inviolable law. Where there is such a recognized sovereign law, monarchy is the most satisfactory type of constitution, democracy the least satisfactory, but where there is no "fundamental law," this situation is inverted. A "sovereign" democracy is preferable to an irresponsible autocrat. The dialogue is rich in thoughts which have passed into the substance of Aris totle's ethics and politics. Aristotle took directly from it the con ception of "politics" as the "architectonic" practical science to which all others are subordinate ; the formula of the "right mean" comes from it together with the Philebus.