Two things fill the mind with ever new and increasing admiration and reverence: the starry heavens above me and the moral law within me.

I had to deny knowledge in order to make room for faith.

Have the courage to use your own understanding!

Treat humanity, in your own person or in another, always as an end and never merely as a means.

You must learn all things: both the steadfast heart of well-rounded Truth and the opinions of mortals, in which there is no true trust.

-- Parmenides

For thinking and Being are the same.

-- Parmenides

Color exists by convention, sweet by convention, bitter by convention; in reality there are only atoms and void.

-- Democritus

I know that I know nothing.

-- Socrates

Imagine prisoners chained underground since childhood, seeing only shadows on a wall and taking them for reality.

-- Plato

All things are ungraspable.

-- Pyrrho