Not ignorance, but ignorance of ignorance, is the death of knowledge.

The guiding motto in the life of every natural philosopher should be, seek simplicity and distrust it.

Art flourishes where there is a sense of adventure.

The point about zero is that we do not need to use it in the operation of daily life. No one goes out to buy zero fish.

It does not matter what men say in words, so long as their activities are controlled by settled instincts. The words may ultimately destroy the instincts; but until this has occurred, words do not count.

Intelligence is quickness to apprehend as distinct form ability, which is capacity to act wisely on the thing apprehended.

In a sense, knowledge shrinks as wisdom grows: for details are swallowed up in principles.