Democritus

Democritus (c.460 – c.370 BC) was an ancient Greek philosopher, and one of the first atheists in history. He offered a materialistic explanation of the world and did not refer to gods or spirits. Democritus and his teacher Leucippus, are credited with the development of the atomic theory. They had absolutely no scientific reason for thinking so but proposed all matter was made of invisible particles, known as atoms.

quotes attributed to Democritus:

Happiness resides not in possessions, and not in gold, happiness dwells in the soul.

Nothing exists except atoms and empty space; everything else is opinion.

Throw moderation to the winds, and the greatest pleasures bring the greatest pains.

Do not trust all men, but trust men of worth; the former course is silly, the latter a mark of prudence.

Everything existing in the universe is the fruit of chance and necessity.

I would rather discover one scientific fact than become King of Persia.

By desiring little, a poor man makes himself rich.

It is greed to do all the talking but not to want to listen at all.

Our sins are more easily remembered than our good deeds.

If thou suffer injustice, console thyself; the true unhappiness is in doing it.