Philebus

SOCRATES: There are some mixtures which are of the body, and only in the body, and others which are of the soul, and only in the soul; while there are other mixtures of pleasures with pains, common both to soul and body, which in their composite state are called sometimes pleasures and sometimes pains.

SOCRATES: Whenever, in the restoration or in the derangement of nature, a man experiences two opposite feelings; for example, when he is cold and is growing warm, or again, when he is hot and is becoming cool, and he wants to have the one and be rid of the other;—the sweet has a bitter, as the common saying is, and both together fasten upon him and create irritation and in time drive him to distraction.

SOCRATES: Of cases in which the pain exceeds the pleasure, an example is afforded by itching, of which we were just now speaking, and by the tingling which we feel when the boiling and fiery element is within, and the rubbing and motion only relieves the surface, and does not reach the parts affected; then if you put them to the fire, and as a last resort apply cold to them, you may often produce the most intense pleasure or pain in the inner parts, which contrasts and mingles with the pain or pleasure, as the case may be, of the outer parts; and this is due to the forcible separation of what is united, or to the union of what is separated, and to the juxtaposition of pleasure and pain.

SOCRATES: Sometimes the element of pleasure prevails in a man, and the slight undercurrent of pain makes him tingle, and causes a gentle irritation; or again, the excessive infusion of pleasure creates an excitement in him,—he even leaps for joy, he assumes all sorts of attitudes, he changes all manner of colours, he gasps for breath, and is quite amazed, and utters the most irrational exclamations.

SOCRATES: He will say of himself, and others will say of him, that he is dying with these delights; and the more dissipated and good-for-nothing he is, the more vehemently he pursues them in every way; of all pleasures he declares them to be the greatest; and he reckons him who lives in the most constant enjoyment of them to be the happiest of mankind.

SOCRATES: Yes, Protarchus, quite true of the mixed pleasures, which arise out of the communion of external and internal sensations in the body; there are also cases in which the mind contributes an opposite element to the body, whether of pleasure or pain, and the two unite and form one mixture. Concerning these I have already remarked, that when a man is empty he desires to be full, and has pleasure in hope and pain in vacuity. But now I must further add what I omitted before, that in all these and similar emotions in which body and mind are opposed (and they are innumerable), pleasure and pain coalesce in one.