To harm another is to harm oneself

Those then who know not wisdom and virtue, and are always busy with gluttony and sensuality, go down and up again as far as the mean; and in this region they move at random throughout life, but they never pass into the true upper world; thither they neither look, nor do they ever find their way, neither are they truly filled with true being, nor do they ever taste of pure and abiding pleasure.

One thing I know, that I know nothing. This is the source of my wisdom.

He said that there was one only good, namely, knowledge; and one only evil, namely, ignorance.

Not I, but the city teaches.

An envious man waxeth lean with the fatness of his neighbors. Envy is the daughter of pride, the author of murder and revenge, the beginner of secret sedition and the perpetual tormentor of virtue. Envy is the filthy slime of the soul; a venom, a poison, or quicksilver which consumeth the flesh and drieth up the marrow of the bones.

Whoever would have his body supple, easy and healthful should learn to dance.