the honourable mind which is to form a healthy judgment should have had no experience or contamination of evil habits when young. And this is the reason why in youth good men often appear to be simple, and are easily practised upon by the dishonest, because they have no examples of what evil is in their own souls.
 Plato, The Republic. copy citation

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Author Plato
Source The Republic
Topic youth evil
Date
Language English
Reference
Note Translated by Benjamin Jowett
Weblink http://www.gutenberg.org/files/1497/1497-h/1497-h.htm

Context

“he ought not therefore to have been trained among vicious minds, and to have associated with them from youth upwards, and to have gone through the whole calendar of crime, only in order that he may quickly infer the crimes of others as he might their bodily diseases from his own self-consciousness; the honourable mind which is to form a healthy judgment should have had no experience or contamination of evil habits when young. And this is the reason why in youth good men often appear to be simple, and are easily practised upon by the dishonest, because they have no examples of what evil is in their own souls. Yes, he said, they are far too apt to be deceived. Therefore, I said, the judge should not be young; he should have learned to know evil, not from his own soul, but from late and long observation of the nature of evil in others:” source