But the difference between Melissus and his master can hardly be said to be a difference of doctrine; point for point, they are identical. The difference is a difference of vision or mental picture as to this mighty All which is One. Melissus, so to speak, places himself at the centre of this Universal being, and sees it stretching out infinitely, unendingly, in space and in time. Its oneness comes to him as the _sum_ of these infinities. Parmenides, on the other hand, sees all these endless immensities as related to a centre; he, so to speak, enfolds them all in the grasp of his unifying thought, and as thus equally and necessarily related to a central unity he pronounces the All a sphere, and therefore limited. The two doctrines, antithetical in terms, are identical in fact. The absolutely unlimited and the absolutely self-limited are only two ways of saying the same thing.
This difference of view or vision Aristotle in the passage quoted expresses as a difference between _thought_ ((Greek) _logos_) and _matter_ ((Greek) _hule_). This is just a form of his own radical distinction between Essence and Difference, Form and Matter, of which much will be said later on. It is like the difference { 49} between Deduction and Induction; in the first you start from the universal and see within it the particulars; in the second you start from the particulars and gather them into completeness and reality in a universal. The substance remains the same, only the point of view is different. To put the matter in modern mathematical form, one might say, The universe is to be conceived as a _sphere_ (Parmenides) of _infinite radius_ (Melissus). Aristotle is not blaming Melissus or praising Parmenides. As for Xenophanes, Aristotle after his manner finds in him the potentiality of both. He is prior both to the process of thought from universal to particular, and to that from particular to universal. He does not argue at all; his function is Intuition. "He looks out on the mighty sky, and says, The One is God."
Melissus applied the results of his analysis in an interesting way to the question already raised by his predecessors, of the trustworthiness of sensation. His argument is as follows: "If there were many real existences, to each of them the same reasonings must apply as I have already used with reference to the one existence. That is to say, if earth really exists, and water and air and iron and gold and fire and things living and things dead; and black and white, and all the various things whose reality men ordinarily assume,--if all these really exist, and our sight and our hearing give us _facts_, then each of these as { 50} really existing must be what we concluded the one existence must be; among other things, each must be unchangeable, and can never become other than it really is. But assuming that sight and hearing and apprehension are true, we find the cold becoming hot and the hot becoming cold; the hard changes to soft, the soft to hard; the living thing dies; and from that which is not living, a living thing comes into being; in short, everything changes, and what now is in no way resembles what was. It follows therefore that we neither see nor apprehend realities.