If you place your head in a lion's mouth, then you cannot complain one day if he happens to bite it off.

Let there be spaces in your togetherness.

All our knowledge begins with the senses, proceeds then to the understanding, and ends with reason. There is nothing higher than reason.

Wrong life cannot be lived rightly.

There are no eternal facts, as there are no absolute truths.

The simple things are also the most extraordinary things, and only the wise can see them.

What's done can't be undone.

If you would take, you must first give, this is the beginning of intelligence.

The greatest minds are capable of the greatest vices as well as of the greatest virtues.

We are all born ignorant, but one must work hard to remain stupid

Without courage, wisdom bears no fruit.

The ultimate authority must always rest with the individual's own reason and critical analysis.

I've never known any trouble than an hour's reading didn't assuage.

None but ourselves can free our minds.

A precedent embalms a principle.

Those who see the invisible can do the impossible.

You can best serve civilization by being against what usually passes for it.

Appearances often are deceiving.

But the fact that some geniuses were laughed at does not imply that all who are laughed at are geniuses. They laughed at Columbus, they laughed at Fulton, they laughed at the Wright brothers. But they also laughed at Bozo the Clown.

The greatest power we have is the power of choice.

Never put off for tomorrow, what you can do today.