A passage from Diogenes Laertius
Diogenes Laertius, Lives of Eminent Philosophers 7.56
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Physics teaches us the nature of the universe, and ethics teaches us how to live. Both are necessary for the good life.
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Take care not to be Caesarified, or dyed with purple; for it does happen. Keep thyself then simple, good, pure, serious, free from affectation.
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It is a man's special privilege to love even those who wrong him.