Plato

Opinion is the medium between knowledge and ignorance.

Thinking: the talking of the soul with itself.

One of the penalties for refusing to participate in politics is that you end up being governed by your inferiors.

There's a victory, and defeat; the first and best of victories, the lowest and worst of defeats which each man gains or sustains at the hands not of another, but of himself.

The measure of a man is what he does with power.

Honesty is for the most part less profitable than dishonesty.

No evil can happen to a good man, either in life or after death.

Tyranny naturally arises out of democracy.

The beginning is the most important part of the work.

People are like dirt. They can either nourish you and help you grow as a person or they can stunt your growth and make you wilt and die.

Wisdom alone is the science of other sciences.

The first and greatest victory is to conquer yourself; to be conquered by yourself is of all things most shameful and vile.

To prefer evil to good is not in human nature; and when a man is compelled to choose one of two evils, no one will choose the greater when he might have the less.

Cunning is but the low mimic of wisdom.

No trace of slavery ought to mix with the studies of the freeborn man. No study, pursued under compulsion, remains rooted in the memory.

Love is the joy of the good, the wonder of the wise, the amazement of the Gods.

Wonder is the feeling of the philosopher, and philosophy begins in wonder.

Wise men speak because they have something to say; Fools because they have to say something.

Courage is knowing what not to fear.

Love is a serious mental disease.