Don't exercise your freedom of speech until you have exercised your freedom of thought.
Each day hands me a clean sheet of paper upon which to write. Therefore, I would be wise to write without ever having the need to erase.
Always count the costs before starting any journey, and never take a step without finding its costs.
Humanity has advanced, when it has advanced, not because it has been sober, responsible, and cautious, but because it has been playful, rebellious, and immature.
May your sleep be your death, and your wakefulness be your heaven.
If a negative viewer looks at you with an ugly fiendish eye, find a way and pluck off his eyes, or better still, protect your good image.
The cautious seldom err.
You don't throw a compass overboard because the ocean is calm.
Don't ever take a fence down until you know why it was put up.
Every sentence I utter must be understood not as an affirmation but as a question.[A caution he gives his students, to be wary of dogmatism.]
If you are too careful, you are so occupied in being careful that you are sure to stumble over something.