Pur. I see now; exchange is the use of a loose instead of a precise expression, while interchange is the use of both expressions, each in the other's place.
Ly. These subtleties are not unpleasing. Similarly, when we are concerned with a person, it is in our own interest; but when we are concerned for him, it is in his. It is true the phrases are sometimes confused, but there are those who observe the distinction; and it is as well to be on the safe side.
Pur. Quite true.
Ly. Now, can you tell me the difference between 'setting' and 'sitting,' or between 'be seated' and 'sit'?
Pur. No; but I have heard you say that 'sit yourself' is a barbarism.
Ly. Yes, quite so; but now I tell you that 'be seated' is not the same as 'sit.'
Pur. Why, what may the difference be?
Ly. When a man is on his legs, you can only tell him to be seated; but if he is seated already, you can tell him to sit still.
Sit where thou art; we find us seats elsewhere. It means 'remain sitting,' you see. Here again we have to say that it is a mistake to reverse the expressions. And as to 'set' and 'sit,' surely it is the whole difference between transitive and intransitive?