“The true Enlightenment thinker, the true rationalist, never wants to talk anyone into anything. No, he does not even want to convince; all the time he is aware that he may be wrong.”
On Freedom (1958)
Context: The true Enlightenment thinker, the true rationalist, never wants to talk anyone into anything. No, he does not even want to convince; all the time he is aware that he may be wrong. Above all, he values the intellectual independence of others too highly to want to convince them in important matters. He would much rather invite contradiction, preferably in the form of rational and disciplined criticism. He seeks not to convince but to arouse — to challenge others to form free opinions.
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Karl Popper 82
Austrian-British philosopher of science 1902–1994Related quotes

“I never do anything I don't want to do. Nor does anyone, but in my case I am always aware of it.”
Source: Stranger in a Strange Land

Conclusion
The Ethics of Ambiguity (1947)
Context: A conquest of this kind is never finished; the contingency remains, and, so that he may assert his will, man is even obliged to stir up in the world the outrage he does not want. But this element of failure is a very condition of his life; one can never dream of eliminating it without immediately dreaming of death. This does not mean that one should consent to failure, but rather one must consent to struggle against it without respite.

“Which perspective is true? he thought. Which do I want to be true?”
Source: Declare (2001), Chapter 10 (p. 285)

"On Freedom" in All Life is Problem Solving (1999)
Context: When I speak of reason or rationalism, all I mean is the conviction that we can learn through criticism of our mistakes and errors, especially through criticism by others, and eventually also through self-criticism. A rationalist is simply someone for whom it is more important to learn than to be proved right; someone who is willing to learn from others — not by simply taking over another's opinions, but by gladly allowing others to criticize his ideas and by gladly criticizing the ideas of others. The emphasis here is on the idea of criticism or, to be more precise, critical discussion. The genuine rationalist does not think that he or anyone else is in possession of the truth; nor does he think that mere criticism as such helps us achieve new ideas. But he does think that, in the sphere of ideas, only critical discussion can help us sort the wheat from the chaff. He is well aware that acceptance or rejection of an idea is never a purely rational matter; but he thinks that only critical discussion can give us the maturity to see an idea from more and more sides and to make a correct judgement of it.