There is no permanent absolute unchangeable truth; what we should pursue is the most convenient arrangement of our ideas.

He was born stupid, and greatly increased his birthright.

Men of Science. If they are worthy of the name they are indeed about God's path and about his bed and spying out all his ways.

Nature. As the word is now commonly used it excludes nature's most interesting productions-the works of man. Nature is usually taken to mean mountains, rivers, clouds and undomesticated animals and plants. I am not indifferent to this half of nature, but it interests me much less than the other half.

Though analogy is often misleading, it is the least misleading thing we have.

Friends are like money, easier made than kept.

You cannot have a thing "matter" by itself which shall have no motion in it, nor yet a thing "motion" by itself which shall exist apart from matter; you must have both or neither. You can have matter moving much, or little, and in all conceivable ways; but you cannot have matter without any motion more than you can have motion without any matter that is moving.