sort of action—to determine that is the difficulty.
Yes, he said; there lies the difficulty.
Then let us now try and determine whether they are the same or different.
How can we? he asked.
The criterion of truth: Nothing can be and not be at the same time in the same relation.
I replied as follows:
The same thing clearly cannot act or be acted upon in the same part or in relation to the same thing at the same time, in contrary ways; and therefore whenever this contradiction occurs in things apparently the same, we know that they are really not the same, but different.
Good.
For example, I said, can the same thing be at rest and in motion at the same time in the same part?
Impossible.
Still, I said,