Socrates, Plato, and Aristotle all criticized the sophists, the traveling professional teachers who taught pupils a variety of subjects, especially rhetoric, the art of persuasive speaking. In many ways they were a diverse lot, often quite knowledgeable in the learning of their day. But they all shared, in varying degrees, an antagonism to the commitments underlying philosophic inquiry as pursued by Socrates, Plato, and Aristotle. What were the issues—at least as we see them in the dialogues of Plato?
1. The sophists taught people how to “make the weaker argument appear the stronger.” They were more interested in winning an argument than in discovering truth.
2. At least one of the sophists entertained radical skepticism. Gorgias wrote (I include only the headlines of the sections of his two-page argument): Nothing exists. If anything exists, it is incomprehensible. If it is comprehensible, it is incommunicable. (See Kathleen Freeman, Ancilla to the Pre-Socratic Philosophers (Cambridge: Harvard University Press, 1962.)
2. The sophists were, in many cases, atheists or agnostics. Protagoras: “About the gods, I am not able to know whether they exist or do not exist, nor what they are like in form; for the factors preventing knowledge are many: the obscurity of the subject, and the shortness of human life.”
3. At least one of the sophists proposed a cynical idea of justice. Thrasymachus, whom we meet in Book I of the Republic, asserted, “Justice is the interest of the stronger.”
4. The sophists tended to believe that values are not real, but merely a matter of the opinion of the individual or the culture, as expressed in the famous line of Protagoras, “Man is the measure . . . .” Socrates and Plato sought for higher standards than simply human opinion. It must be possible to raise questions, to criticize the opinion of any person or culture. If human opinion is the highest standard, then such criticism is impossible. Therefore philosophy—for Socrates and Plato—calls for inquiry in search of meanings and values (such as beauty and goodness) that are real.
5. Some sophists (and most pre-Socratic philosophers) centered their thinking on speculations about nature or other subjects rather than on cultivating the mind in ways that would help develop an excellent character.
Here is one surviving fragment written by Gorgias of Leontini, a sophist who lived in the latter half of the 5th century BCE, translated by Kathleen Freeman in Ancilla to the Pre-Socraticc Philosophers (Cambridge: Harvard University Press, 1962), pp. 128-29.
I. Nothing exists.
(a) Not-Being does not exist.
(b) Being does not exist.
i. as everlasting
ii. as created.
iii. as both.
iv. as One.
v. as Many.
(c) A mixture of Being and Not-Being does not exist.
II. If anything exists, it is incomprehensible.
III. If it is comprehensible, it is incommunicable.
I. Nothing exists.
If anything exists, it must be either Being or Not-Being, or both Being and Not-Being.
(a) It cannot be Not-Being, for Not-Being does not exist; if it did, it would be at the same time Being and Not-Being, which is impossible.
(b) It cannot be Being, for Being does not exist. If Being exists, it must be either everlasting, or created, or both.
i. It cannot be everlasting; if it were, it would have no beginning, and therefore would be boundless; if it is boundless, then it has no position, for if it had position it would be contained in something, and so it would not longer be boundless; for that which contains is greater than that which is contained, and nothing is greater than the boundless. It cannot be contained by itself, for then the thing containing and the thing contained would be the same, and Being would become two things—both position and body—which is absurd. Hence if Being is everlasting, it is boundless; if boundless, it has no position (‘is nowhere’); if without position, it does not exist.
ii. Similarly, Being cannot be created; if it were, it must come from something, either Being or Not-Being, both of which are impossible.
iii. Similarly, Being cannot be both everlasting and created, since they are opposite. Therefore Being does not exist.
iv. Being cannot be One, because if it exists it has size, and is therefore infinitely divisible; at least it is threefold, having length, breadth and depth.
v. It cannot be Many, because the Many is made up of an addition of Ones, so that since the One does not exist, the Many do not exist either.
(c) A mixture of Being and Not-Being is impossible. There since Being does not exist, nothing exists.
II. If anything exists, it is incomprehensible.
If the concepts of the mind are not realities, reality cannot be thought: if the thing thought is white, then white is thought about; if the thing thought is non-existent, then non-existence is thought about; this is equivalent to saying that ‘existence, reality, is not thought about, cannot be thought.’ Many things thought about are not realities: we can conceive of a chariot running on the sea, or a winged man. Also, since things seen are the objects of sight, and things heard are the objects of hearing, and we accept as real things seen without their being heard, and vice versa; so we would have to accept things thought without their being seen or heard; but this would mean believing in things like the chariot racing on the sea.
Therefore reality is not the object of thought, and cannot be comprehended by it. Pure mind, as opposed to sense-perception, or even as an equally valid criterion, is a myth.
III. If anything is comprehensible, it is incommunicable.
The things which exist are perceptibles; the objects of sight are apprehended by sight, the objects of hearing by hearing, and there is no interchange; so that these sense perceptions cannot communicate with one another. Further, that with which we communicate is speech, and speech is not the same thing as the things that exist, the perceptibles; so that we communicate not the things which exist, but only speech; just as that which is seen cannot become that which is heard, so our speech cannot be equated with that which exists, since it is outside us. Further, speech is composed from the percepts which we receive from without, that is, from perceptibles; so that it is not speech which communicates perceptibles, but perceptibles which create speech. Further, speech can never exactly represent perceptibles, since it is different from them, and perceptibles are apprehended each by the one kind of organ, speech by another. Hence, since the objects of sight cannot be presented to any other organ but sight, and the different sense-organs cannot give their information to one another, similarly speech cannot give any information about perceptibles.
There, if anything exists and is comprehended, it is incommunicable.