“We cannot wait until we agree upon the truths of a new social theory to think and act as democratic experimentalists. We must find the ideas our efforts and commitments require, and try to make no assumptions that the facts of social reality and historical experience invalidate.”

Source: A Theory of Justice (1971; 1975; 1999), Chapter III, Section 28, pg. 171

The Downing Street Years (1993)

1960, The New Frontier
Context: For the harsh facts of the matter are that we stand on this frontier at a turning-point in history. We must prove all over again whether this nation — or any nation so conceived — can long endure — whether our society — with its freedom of choice, its breadth of opportunity, its range of alternatives — can compete with the single-minded advance of the Communist system. Can a nation organized and governed such as ours endure? That is the real question. Have we the nerve and the will? Can we carry through in an age where we will witness not only new breakthroughs in weapons of destruction — but also a race for mastery of the sky and the rain, the ocean and the tides, the far side of space and the inside of men's minds? Are we up to the task — are we equal to the challenge? Are we willing to match the Russian sacrifice of the present for the future — or must we sacrifice our future in order to enjoy the present? That is the question of the New Frontier. That is the choice our nation must make — a choice that lies not merely between two men or two parties, but between the public interest and private comfort — between national greatness and national decline — between the fresh air of progress and the stale, dank atmosphere of "normalcy" — between determined dedication and creeping mediocrity. All mankind waits upon our decision. A whole world looks to see what we will do. We cannot fail their trust, we cannot fail to try.

Source: A Brief History of Time (1988), Ch. 1
Context: Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory. As philosopher of science Karl Popper has emphasized, a good theory is characterized by the fact that it makes a number of predictions that could in principle be disproved or falsified by observation. Each time new experiments are observed to agree with the predictions the theory survives, and our confidence in it is increased; but if ever a new observation is found to disagree, we have to abandon or modify the theory.

Source: The State of the World 2010, public lecture in New York City, USA, (July 2010)

Source: Everyday Grace: Having Hope, Finding Forgiveness And Making Miracles

Source: Caritas Oceania: united by faith and the ocean https://www.vaticannews.va/en/church/news/2021-07/caritas-oceania-annual-forum-interview-cardinal-mafi-tonga.html (31 July 2021)

Source: What Should Legal Analysis Become? (1996), p. 20