“Memory is a complicated thing, a relative to truth, but not its twin.”

"The Mathematician", in The Works of the Mind (1947) edited by R. B. Heywood, University of Chicago Press, Chicago
Context: I think that it is a relatively good approximation to truth — which is much too complicated to allow anything but approximations — that mathematical ideas originate in empirics. But, once they are conceived, the subject begins to live a peculiar life of its own and is … governed by almost entirely aesthetical motivations. In other words, at a great distance from its empirical source, or after much "abstract" inbreeding, a mathematical subject is in danger of degeneration. Whenever this stage is reached the only remedy seems to me to be the rejuvenating return to the source: the reinjection of more or less directly empirical ideas.

Satyre III (c. 1598)

Sucesivos Escolios a un Texto Implícito (1992)

Materialism and Empirio-Criticism (1908)

Source: Carpe Jugulum

Light (1919), Ch. XVI - De Profundis Clamavi

"Building a Moral Society", Chamberlin Lecture at Lewis & Clark College (1995)
Context: An immoral society betrays humanity because it betrays the basis for humanity, which is memory. An immoral society deals with memory as some politicians deal with politics. A moral society is committed to memory: I believe in memory. The Greek word alethia means Truth, Things that cannot be forgotten. I believe in those things that cannot be forgotten and because of that so much in my work deals with memory... What do all my books have in common? A commitment to memory.

The Transcendent Unity of Religions (1953; revised edition 1984)

The Riverworld series, Gods of Riverworld (1983)
Context: The truth is that you can be immortal, relatively so, anyway. You won't last beyond the death of the universe and probably not nearly as long as the universe does. But you have the potentiality for living a million years, two, perhaps three or more. As long as you can find a Terrestrial-type planet with a hot core and have resurrection machinery available.
Unfortunately, not all can be permitted to possess immortality. Too many would make immortality miserable or hellish for the rest, and they would try to control others through their control of the resurrection machinery. Even so, everybody, without exception, is given a hundred years after his Earthly death to prove that he or she can live peacefully and in harmony with himself and the others, within the tolerable limits of human imperfections. Those who can do this will be immortal after the two projects are completed.