“There is one thing, and only one, in the whole universe which we know more about than we could learn from external observation. That one thing is Man. We do not merely observe men, we are men. In this case we have, so to speak, inside information; we are in the know.”
Book I, Chapter 4, "What Lies behind the Law"
Mere Christianity (1952)
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Clive Staples Lewis 272
Christian apologist, novelist, and Medievalist 1898–1963Related quotes

The Elements of Morality, Book 1, ch. 1. (1845).

Entry (1955)
Eric Hoffer and the Art of the Notebook (2005)
Context: Our doubts about ourselves cannot be banished except by working at that which is the one and only thing we know we ought to do. Other people's assertions cannot silence the howling dirge within us. It is our talents rusting unused within us that secrete the poison of self-doubt into our bloodstream.

“The universe as we know it is a joint product of the observer and the observed.”
Variant: The universe as we know it is a joint product of the observer and the observed.
Pierre Teilhard de Chardin

Source: Simone Weil : An Anthology (1986), Attention and Will (1947), p. 216

“The one thing we know today is we can't continue to do business the way we have in the past.”

Source: Nature of Man and His Government (1959), p. 81