Heraclitus, though influenced by the Milesians, cannot be said to belong to any "school." Another "school" however, known as the Eleatic, now arose in the Greek West. The founder of this school was Parmenides, a native of the Greek city of Elea in southern Italy. He is said to have made laws, which were greatly respected, for his native city, and to have come to Athens in his sixty-fifth year and conversed with the young Socrates. This must have been in about 450 B.C. He is said too to have been converted to the philosophical way of life by a Pythagorean to whom he afterwards built a shrine as a hero. He wrote in verse and, though from a literary point of view his verse is less "poetical" than the prose of Heraclitus, it is verse of considerable fervour. Quite obviously the philosophical way of life means much to him, though it does not mean what it meant to Pythagoras or what, later, it was to mean to Lucretius. Parmenides seems unique in having been inspired with rapture by pure logic. He was the first logician and may be described as the first philosopher in the modern sense of the word. His system depends entirely on logical deduction and has little or nothing in common with the speculative "science" of the Milesians or with what (for want of a better word) we may call the intuitive method of Heraclitus. It is to be noted that Plato, with his own respect for method, takes Parmenides more seriously than any of his predecessors.
Parmenides' poem begins with an allegorical description of his journey by chariot from the abode of Night to that of Day. Here he is met by a goddess (he is "a youth" at the time) who defines for him the methods of thought and introduces him to the Way of Truth. The second part of the poem, "The Way of Opinion," merely describes the views of others. As Parmenides did not believe in them himself, we shall only be concerned with the first part.
Here he (or the goddess) distinguishes between three ways of thought. They are (1) that It is, (2) that It is not, (3) that It both is and is not. (3) must obviously refer to the method of Heraclitus. Parmenides vigorously asserts that the only possible way of thought is (1). It is impossible, he says, to think or to believe in "nothing" as something which exists. There cannot "be" such a thing as emptiness. There can be no spaces between objects, no temporal beginnings or endings of things. The universe is one single, continuous object. Motion and change are inconceivable, and, if our senses suggest that things do move and do change, then our senses are deceiving us.
We may perhaps explain the doctrine of "that It is" more clearly by using rather more modern terms. The basic idea is this: (1) Any intelligible name must be the name of something which exists. (This idea, incidentally, is common in philosophy well into the twentieth century.) (2) Therefore a sentence of the form "— does not exist" must always be meaningless or self-contradictory. It is meaningless if the blank is filled by what is not a name of something existing; it is contradictory if it is filled by a real name. (3) Therefore all views must be rejected which "either say or imply that something (anything) does not exist; for that "cannot be thought."
It follows that what exists must be temporally infinite; to say otherwise would entail referring to "what is not" as preceding and following it, and that makes no sense. Spatially it is concluded that "what exists" is finite and spherical, though it is rather difficult to see why Parmenides believed this. Presumably it was because "bounded by nothing" was to him a meaningless idea; yet it seems that is could also be taken as a reason for denying that "what exists" is spatially bounded at all.
Now there is something quite new in this rigid, and enthusiastic, application of a supposed principle of logic, leading, as it does, to such startling conclusions as that change and motion are illusions of the senses. The conclusions are shown in their most striking form by Parmenides' follower Zeno in his famous paradoxes. The logical method, however — a method which depends entirely on thought and not at all on experiment or observation — is the creation of Parmenides. I am quoting from Burnet the passages from the poem which define the doctrine of "that It is."
One path only is left for us to speak of, namely, that It is. In this path are very many tokens that what is is uncreated and indestructible; for it is complete, immovable, and without end. Nor was it ever, nor will it be; for now it is, all at once, a continuous one. For what kind of origin for it wilt thou look for? In what way and from what source could it have drawn its increase? . . . I shall not let thee say nor think that it came from what is not; for it can neither be thought nor uttered that anything is not. And, if it came from nothing, what need could have made it arise later rather than sooner? Therefore must it either be altogether or be not at all. Nor will the force of truth suffer aught to arise besides itself from that which is not. Wherefore, Justice doth not loose her fetters and let anything come into being or pass away, but holds it fast. Our judgment thereon depends on this: "Is it or is it not?" Surely it is adjudged, as it needs must be, that we are to set aside the one way as unthinkable and nameless (for it is no true way), and that the other path is real and true. How, then, can what is be going to be in the future? Or how could it come into being? If it came into being, it is not; nor is it if it is going to be in the future. Thus is becoming extinguished and passing away not to be heard of.
Nor is it divisible, since it is all alike, and there is no more of it in one place than in another, to hinder it from holding together, nor less of it, but everything is full of what is. Wherefore it is wholly continuous; for what is, is in contact with what is.
Moreover, it is immovable in the bonds of mighty chains, without beginning and without end; since coming into being and passing away have been driven afar, and true belief has cast them away. It is the same, and it rests in the self-same place, abiding in itself. And thus it remaineth constant in its place; for hard necessity keeps it in the bonds of the limit that holds it fast on every side. Wherefore it is not permitted to what is to be infinite; for it is in need of nothing; while, if it were infinite, it would stand in need of everything.
The thing that can be thought and that for the sake of which the thought exists is the same; for you cannot find thought without something that is, as to which it is uttered. And there is not, and never shall be, anything besides what is, since fate has chained it so as to be whole and immovable. Wherefore all these thing are but names which mortals have given, believing them to be true — coming into being and passing away, being and not being, change of place and alteration of bright colour.
Since, then, it has a furthest limit, it is complete on every side, like the mass of a rounded sphere, equally poised from the centre in every direction; for it cannot be greater or smaller in one place than in another. For there is nothing that could keep it from reaching out equally, nor can aught that is to be be more here and less there than what is, since it is all inviolable. For the point from which it is equal in every direction tends equally to the limits.