Mankind must put an end to war or war will put an end to mankind.

I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the Earth. No single space project in this period will be more impressive to mankind, or more important for the long-range exploration of space; and none will be so difficult or expensive to accomplish. Speech to Special Joint Session of Congress (25 May 1961)

A scientist has to prove every day that he belongs to the human part of mankind. Address to the United Nations General Assembly (25 September 1961)