When I consider this carefully, I find not a single property which with certainty separates the waking state from the dream. How can you be certain that your whole life is not a dream?

We do not describe the world we see, we see the world we can describe.

Whenever anyone has offended me, I try to raise my soul so high that the offense cannot reach it.

De omnibus dubitandum

Divide each difficulty into as many parts as is feasible and necessary to resolve it.

Conquer yourself rather than the world.

The reading of all good books is like a conversation with the finest minds of past centuries.

The chief cause of human errors is to be found in the prejudices picked up in childhood.

Doubt is the origin of wisdom

The only thing we have power over in the universe is our own thoughts.

How can you be certain that your whole life is not a dream?

We must be kind and gentle gardeners with people and nature.

There comes a time when a man must stand up and do what he knows is Wrong.

[Pure research] is worth every penny it costs.

The most revolutionary invention of the Nineteenth Century was the artificial sterilization of marriage.

There is music wherever there is rhythm, as there is life wherever there beats a pulse.

There's nothing more interesting than the landscape of the human face.

I wish that we worried more about asking the right questions instead of being so hung up on finding answers.

I say personally because I am 84 years old, and [Barack Obama's] is the first administration that has scared me in terms of my lifespan.

Of two Evils we take the less.

The past does not influence me; I influence it.