1. By the "imperfect" or "partial" followers of Socrates we mean those of his disciples who, failing to comprehend the whole mind of their master, addressed themselves to one or other of the special points of his teaching, which they developed to the exclusion of the others. Two characteristics, we have observed, were strongly marked in the teaching of Socrates, the dialectical and the ethical. The former we may call the operative element in the instructions of Socrates, the latter the result in which his instructions culminated. These two elements became separated in the teaching of the "imperfectly Socratic" philosophers. One class devoted themselves mainly to the development of the dialectical side of the teaching of Socrates, the other gave exclusive prominence to the ethical, which they strove to develop in conjunction with certain principles borrowed from the pre-Socratic schools. To the first class belong the Megaric or Eristic, and the Elian or Eretrian Schools; to the second, the School of the Cynics, and the Cyrenaic or Hedonist School.
§ 25.
The founder of the Megaric or Eristic School was Euclid of Megara, who must not be confounded with the Alexandrian mathematician of the same name, who lived a century later. The story is told of him that in order to enjoy the society of Socrates he often came to Athens in the gloom of the evening, at the time when the Athenians had forbidden the Megarians, under pain of death, to enter Athens. He was present at the death of Socrates (Phaed. p. 59, C). Soon after, the greater number of the disciples of Socrates quitted Athens to join him at Megara. He appears to have lived for several decades after the death of Socrates at the head of the school which he had founded.
2. The main end of the teaching of Euclid seems to have been to combine the ethical views of Socrates with the Eleatic theory of the One. Adopting unreservedly the principle of Parmenides, he represents the One, not under the concept of Being, but under the Socratic concept of the Good. Socrates had made the knowledge of the Good the basis and the principle of our moral life; Euclid gave an objective subsistence to this concept of the Good, and made the Good the only thing existent. He, accordingly, lays down the principle: The Good is One, though it is called by many names, such as Intelligence, God, Reason. Whatever is opposed to the Good, is non-existent. The Good is unchangeable.
3. This fundamental principle the Megarians tried, after the manner of the Eleatics, to establish by indirect demonstration. Dialectic best served their purposes in such an attempt. Hence they were led to give it special prominence in their teaching. They endeavoured, by dialectical devices, to show that merely empirical knowledge abounds in real or apparent contradictions, and that our notions of things, derived from mere experience, are wholly untenable. They thus sought to establish the Oneness of all Being in the Good by a method wholly similar to that of the Eleatics. This sophistical procedure procured for their teaching the name "Eristic" (doctrine which contends against current opinions). The denial of the Many led them to the further view that there is no diversity between concepts; that the so-called difference between concepts is only a difference between the names of the One, or the Good, and that we have, consequently, no right to speak of one thing as differing from another.
4. The most remarkable of the followers of Euclid were Eubulides the Milesian, and Alexinus, noted for their invention of the sophistical arguments known as "the Liar," "the Concealed," "the Heap of Corn," "the Horned Man," "the Bald-head" (Diog. Laert. II. 108), and Diodorus Cronus, who brought forward new arguments against motion, and who also maintained the view that the necessary alone is real, and the real alone is possible. Stilpo of Megara combined the Megaric doctrines with those of the Cynics. He combated the doctrine of Ideas. To him is ascribed the dialectical theory that a thing can be predicated only of itself, and the ethical principle that the wise man is superior to pain, and that the goal of all moral effort is Insensibility (apatheia). Stilpo is the most famous of the Megarians; he won renown not alone by his philosophy, but also by his firmness of character, his indifference to worldly possessions, his moderation, his evenness of temper, and his activity in public life.
5. The Elian or Eretrian School is another branch of the Megaric Philosophy. This school was founded by Phaedo of Elis, a favourite disciple of Socrates -- the same whom Plato, in the dialogue named after him, introduces as communicating to his friend Echecrates the last discourses of Socrates. After the death of his master he founded in his native city a school of philosophy, which seems to have had much in common with the Megarians. Menedemus, the Eretrian, a pupil of Phaedo (352-278) transferred this school to Eretria, whence its later name. Soon after his death this school, like the Megaric, was absorbed by the Stoa.
6. We have little information regarding Phaedo's doctrines. Of Menedemus, we are told by Diogenes Laertius (II. 135), that he shared the views of Plato, but that he employed Dialectic only to play with it. Like the Megarians, the Eretrians declared Intelligence to be the only good. This is virtue also. Virtue, therefore, is one, as the Good is one.