The evil is that when the feeling of pleasure or pain is most intense, every soul of man imagines the objects of this intense feeling to be then plainest and truest
 Plato, Phaedo. copy citation

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Author Plato
Source Phaedo
Topic pain evil
Date
Language English
Reference
Note Translated by Benjamin Jowett
Weblink http://www.gutenberg.org/files/1658/1658-h/1658-h.htm

Context

“reflecting that when a man has great joys or sorrows or fears or desires, he suffers from them, not merely the sort of evil which might be anticipated—as for example, the loss of his health or property which he has sacrificed to his lusts—but an evil greater far, which is the greatest and worst of all evils, and one of which he never thinks. What is it, Socrates? said Cebes. The evil is that when the feeling of pleasure or pain is most intense, every soul of man imagines the objects of this intense feeling to be then plainest and truest: but this is not so, they are really the things of sight. Very true. And is not this the state in which the soul is most enthralled by the body? How so? Why, because each pleasure and pain is a sort of nail which nails and rivets the soul to the body, until she becomes like the body, and believes that to be true which the body affirms to be true;” source