Then now let us return to the previous discussion. Is that idea or essence, which in the dialectical process we define as essence or true existence—whether essence of equality, beauty, or anything else—are these essences, I say, liable at times to some degree of change? or are they each of them always what they are, having the same simple self-existent and unchanging forms, not admitting of variation at all, or in any way, or at any time?
They must be always the same, Socrates, replied Cebes.
And what would you say of the many beautiful—whether men or horses or garments or any other things which are named by the same names and may be called equal or beautiful,—are they all unchanging and the same always, or quite the reverse? May they not rather be described as almost always changing and hardly ever the same, either with themselves or with one another?
The latter, replied Cebes; they are always in a state of change.
And these you can touch and see and perceive with the senses, but the unchanging things you can only perceive with the mind—they are invisible and are not seen?
That is very true, he said.
Well, then, added Socrates, let us suppose that there are two sorts of existences—one seen, the other unseen.
Let us suppose them.
The seen is the changing, and the unseen is the unchanging?
That may be also supposed.