The Republic - pg. 267

"Then would you be surprised if those who are inexperienced
in truth also have unhealthy opinion about many other things
and are disposed toward pleasure and pain and what's between
them in such a way that, when they are brought to the painful,
they suppose truly and are really in pain, but, when brought
from the painful to the in-between, they seriously suppose they
have come to fulfillment and pleasure; and, as though out of
luck of experience of pleasure they look from pain to the painless
and are deceived?"