“Anything that is conceivable is possible.”

“There is nothing constant in the universe. All ebb and flow, and every shape that's born, bears in its womb the seeds of change.”

“Mankind owns its destiny, and its destiny is the earth. We are destroying it until we have no destiny.”

“We can't control our destiny, but we can control who we become.”

“If we could but recognize our common humanity, that we do belong together, that our destinies are bound up in one another's, that we can be free only together, that we can be human only together, then a glorious world would come into being where all of us lived harmoniously together as members of one family, the human family.”

“A wise man proportions his belief to the evidence.”

“All knowledge degenerates into probability.”