“Reason is like an open secret that can become known to anyone at any time; it is the quiet space into which everyone can enter through his own thought.”
As quoted in Philosophy for a Time of Crisis : An Interpretation, with Key Writings by Fifteen Great Modern Thinkers (1959) by Adrienne Koch, Ch. 18, "Karl Jaspers : A New Humanism"
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Karl Jaspers 44
German psychiatrist and philosopher 1883–1969Related quotes

Dissenting, Osborn v. United States, 385 U.S. 341 (1966)
Judicial opinions
Improvisation for the Theater (1963), page 3
Context: Everyone can act. Everyone can improvise. Anyone who wishes to can play in the theater and learn to become 'stage-worthy.' We learn through experience and experiencing, and no one teaches anyone anything. This is as true for the infant moving from kicking and crawling to walking as it is for the scientist with his equations. If the environment permits it, anyone can learn whatever he chooses to learn; and if the individual permits it, the environment will teach him everything it has to teach. 'Talent' or 'lack of talent' have little to do with it.

晉譯華嚴經疏序 Hwaeomgyeong so seo (Preface to the Commentary on the Jin Translation of the Flower Ornament Sutra)
Translated by A. Charles Muller.

“Anyone can insult a boxer, but not everyone will manage to apologise in time.”
Source: [Афоризми відомих українців, Folio, 2009, 978-966-03-4817-2, Kharkiv, 86, uk]
Source: They'd Rather Be Right (1954), p. 180.