“[T]he only meaning of life worth caring about is one that can withstand our best efforts to examine it.”

Source: Science in a Free Society (1978), p. 184.

Speech in Stourport (12 January 1925), quoted in On England, and Other Addresses (1926), pp. 15-16.
1925
Context: If there is anything... it is my training, which has given me, whether I can use it or not, a knowledge and a sympathy very difficult for any man to attain who has had an exclusively political training I regard it as of the greatest value to myself that during the formative years of my life, and during the ten and twenty years when I first started work in the world, I worked in close contact with all classes of people in this country, and enjoyed, through no credit to myself, the goodwill which I have inherited from generations that have gone before me and left behind a name for honesty, fair play, right judgment, and kindliness to those with whom they worked. Through that, whether I succeed or not, I believe I have an understanding of the mind of the people of the country which I could have gained in no other way. It is through this that I have that ineradicable belief and faith in our people which sustains me through good times and evil, and it is because of this that I have every confidence that, whatever troubles may come to this country, or in this country at any time, the native strength and virtue of our people will overcome everything. There is only one thing which I feel is worth giving one's whole strength to, and that is the binding together of all classes of our people in an effort to make life in this country better in every sense of the word. That is the main end and object of my life in politics.

Source: Story: Substance, Structure, Style, and the Principles of Screenwriting

Source: The Phantom Tollbooth

The Powerbook (2000)

Source: The Expanse, Abaddon's Gate (2013), Chapter 39 (p. 398)

1900s, A Square Deal (1903)
Context: Among ourselves we differ in many qualities of body, head, and heart; we are unequally developed, mentally as well as physically. But each of us has the right to ask that he shall be protected from wrong-doing as he does his work and carries his burden through life. No man needs sympathy because he has to work, because he has a burden to carry. Far and away the best prize that life offers is the chance to work hard at work worth doing; and this is a prize open to every man, for there can be no better worth doing than that done to keep in health and comfort and with reasonable advantages those immediately dependent upon the husband, the father, or the son. There is no room in our healthy American life for the mere idler, for the man or the woman whose object it is throughout life to shirk the duties which life ought to bring. Life can mean nothing worth meaning, unless its prime aim is the doing of duty, the achievement of results worth achieving.

Newsweek interview (2004)

Introductory
The Grammar of Science (1900)