Socrates: And the class to which pleasure belongs has also been long ago discovered?
Protarchus: Yes.
Socrates: And let us remember, too, of both of them, (1) that mind was akin to the cause and of this family; and (2) that pleasure is infinite and belongs to the class which neither has, nor ever will have in itself, a beginning, middle, or end of its own.
Protarchus: I shall be sure to remember.
Socrates: We must next examine what is their place and under what conditions they are generated. And we will begin with pleasure, since her class was first examined; and yet pleasure cannot be rightly tested apart from pain.
Protarchus: If this is the road, let us take it.
Socrates: I wonder whether you would agree with me about the origin of pleasure and pain.
Protarchus: What do you mean?
Socrates: I mean to say that their natural seat is in the mixed class.
Protarchus: And would you tell me again, sweet Socrates, which of the aforesaid classes is the mixed one?
Socrates: I will, my fine fellow, to the best of my ability.
Protarchus: Very good.
Socrates: Let us then understand the mixed class to be that which we placed third in the list of four.
Protarchus: That which followed the infinite and the finite; and in which you ranked health, and, if I am not mistaken, harmony.
Socrates: Capital; and now will you please to give me your best attention?
Protarchus: Proceed; I am attending.
Socrates: I say that when the harmony in animals is dissolved, there is also a dissolution of nature and a generation of pain.
Protarchus: That is very probable.
Socrates: And the restoration of harmony and return to nature is the source of pleasure, if I may be allowed to speak in the fewest and shortest words about matters of the greatest moment.
Protarchus: I believe that you are right, Socrates; but will you try to be a little plainer?
Socrates: Do not obvious and everyday phenomena furnish the simplest illustration?
Protarchus: What phenomena do you mean?
Socrates: Hunger, for example, is a dissolution and a pain.
Protarchus: True.
Socrates: Whereas eating is a replenishment and a pleasure?