The reflection of Parmenides takes its rise from observation of the transitoriness and changeableness of things. The world, as we know it, is a world of change and mutation. All things arise and pass away. Nothing is permanent, nothing stands. One moment it is, another moment it is not. It is as true to say of {44} anything, that it is not, as that it is. The truth of things cannot lie here, for no knowledge of that which is constantly changing is possible. Hence the thought of Parmenides becomes the effort to find the eternal amid the shifting, the abiding and everlasting amid the change and mutation of things. And there arises in this way the antithesis between Being and not-being. The absolutely real is Being. Not-being is the unreal. Not-being is not at all. And this not-being he identifies with becoming, with the world of shifting and changing things, the world which is known to us by the senses. The world of sense is unreal, illusory, a mere appearance. It is not-being. Only Being truly is. As Thales designated water the one reality, as the Pythagoreans named number, so now for Parmenides the sole reality, the first principle of things, is Being, wholly unmixed with not-being, wholly excludent of all becoming. The character of Being he describes, for the most part, in a series of negatives. There is in it no change, it is absolutely unbecome and imperishable. It has neither beginning nor end, neither arising nor passing away. If Being began, it must have arisen either from Being or from not-being. But for Being to arise out of Being, that is not a beginning, and for Being to arise out of not-being is impossible, since there is then no reason why it should arise later rather than sooner. Being cannot come out of not-being, nor something out of nothing. _Ex nihilo nihil fit_. This is the fundamental thought of Parmenides. Moreover, we cannot say of Being that it was, that it is, that it will be. There is for it no past, no present, and no future. It is rather eternally and timelessly present. It is undivided and indivisible. For anything to be divided {45} it must be divided by something other than itself. But there is nothing other than Being; there is no not-being. Therefore there is nothing by which Being can be divided. Hence it is indivisible. It is unmoved and undisturbed, for motion and disturbance are forms of becoming, and all becoming is excluded from Being. It is absolutely self-identical. It does not arise from anything other than itself. It does not pass into anything other than itself. It has its whole being in itself. It does not depend upon anything else for its being and reality. It does not pass over into otherness; it remains, steadfast, and abiding in itself. Of positive character Being has nothing. Its sole character is simply its being. It cannot be said that it is this or that; it cannot be said that it has this or that quality, that it is here or there, then or now. It simply _is_.