There is no higher or lower knowledge, but one only, flowing out of experimentation.

Oysters open completely when the moon is full; and when the crab sees one it throws a piece of stone or seaweed into it and the oyster cannot close again so that it serves the crab for meat. Such is the fate of him who opens his mouth too much and thereby puts himself at the mercy of the listener.

Those who are enamoured of practice without science are like a pilot who goes into a ship without rudder or compass and never has any certainty of where he is going. Practice should always be based upon a sound knowledge of theory.

Knowledge ... shall always bear witness like a clarion to its creator.

Having wandered some distance among gloomy rocks, I came to the entrance of a great cavern ... Two contrary emotions arose in me: fear and desire--fear of the threatening dark cavern, desire to see whether there were any marvelous things in it.

I have been impressed with the urgency of doing.

We must doubt the certainty of everything which passes through the senses, but how much more ought we to doubt things contrary to the senses, such as the existence of God and the soul.