"Any one, if he will only observe, can find some little thing he does not understand as a starter for an investigation."

"A man, as a general rule, owes very little to what he is born with — a man is what he makes of himself."

"A man's own judgement should be the final appeal in all that relates to himself."

"Man is a tool-using animal. Without tools he is nothing, with tools he is all."

"The best way to predict the future is to invent it."