Oratory is good only if it has the qualities of fitness for the occasion, propriety of style, and originality of treatment, while in the case of letters there is no such need whatsoever.
IsocratesAbhor flatterers as you would deceivers; for both, if trusted, injure those who trust them. If you admit as friends men who seek your favor for the lowest ends, your life will be lacking in friends who will risk your displeasure for the highest good.
IsocratesRegard as your most faithful friends, not those who praise everything you say or do, but those who criticize your mistakes.
Isocrates