Parmenides (160)

The others are, then, not like nor unlike nor both. For if they were like or unlike, they would partake of one of the two elements, and if they were both, of the two opposites and that was shown to be impossible.

True.

They are, then, neither the same nor other, nor in motion nor at rest, nor becoming nor being destroyed, nor greater nor less nor equal, and they experience no similar affections; for if the others are subject to such affections, they will participate in one and two and three and odd and even, in which we saw that they cannot participate, if they are in every way utterly deprived of unity.

Very true.

Therefore if one exists, the one is all things and nothing at all in relation both to itself and to all others.

Perfectly true.

Well, and ought we not next to consider what must happen if one does not exist?

Yes, we ought.

What, then, is the sense of this hypothesis—if one does not exist?

Is it different in any way from this—if not one does not exist?

Certainly it is different.

Is it merely different, or are the two expressions—if not one does not exist and if one does not exist—complete opposites?

They are complete opposites.

Now if a person should say if greatness does not exist, if smallness does not exist, or anything of that sort, would he not make it clear that in each case the thing he speaks of as not existing is different?

Certainly.

And in our case does he not make it clear that he means, when he says if one is not, that the thing which is not is different from other things, and do we not know what he means?

Yes, we do know.

In the first place, then, he speaks of something which is known, and secondly of something different from other things, when he says one, whether he adds to it that it is or that it is not; for that which is said to be non-existent is known none the less, and is known to be different from other things, is it not?

Certainly.

Then we should begin at the beginning by asking: if one is not, what must follow? In the first place this must be true of the one, that there is knowledge of it, or else not even the meaning of the words if the one does not exist would be known.

True.

And is it not also true that the others differ from the one, or it cannot be said to differ from the others?

Certainly.

Then a difference belongs to the one in addition to knowledge; for when we say that the one differs from the others, we speak of a difference in the one, not in the others.

That is clear.

And the non-existent one partakes of that and some and this and relation to this and these and all notions of that sort; for the one could not be spoken of, nor could the things which are other than one, nor could anything in relation to the one or belonging to it be or be spoken of, if the one did not partake of the notion some or of those other notions.

True.