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Karl Popper Quotes
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Sir Karl Raimund Popper was an Austrian-British philosopher and professor.Generally regarded as one of the 20th century's greatest philosophers of science, Popper is known for his rejection of the classical inductivist views on the scientific method in favour of empirical falsification. A theory in the empirical sciences can never be proven, but it can be falsified, meaning that it can and should be scrutinised by decisive experiments. Popper is also known for his opposition to the classical justificationist account of knowledge, which he replaced with critical rationalism, namely "the first non-justificational philosophy of criticism in the history of philosophy".In political discourse, he is known for his vigorous defence of liberal democracy and the principles of social criticism that he came to believe made a flourishing open society possible. His political philosophy embraces ideas from all major democratic political ideologies and attempts to reconcile them, namely socialism/social democracy, libertarianism/classical liberalism and conservatism.

✵ 28. July 1902 – 17. September 1994
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Karl Popper: 82 quotes51 likes

Karl Popper Quotes

“Whenever a theory appears to you as the only possible one, take this as a sign that you have neither understood the theory nor the problem which it was intended to solve.”

Karl Popper

Objective Knowledge: An Evolutionary Approach (1972)

“For it was my master who taught me not only how very little I knew but also that any wisdom to which I might ever aspire could consist only in realizing more fully the infinity of my ignorance.”

Karl Popper

“Good tests kill flawed theories; we remain alive to guess again.”

Karl Popper

As quoted in My Universe : A Transcendent Reality (2011) by Alex Vary, Part II

“We must plan for freedom, and not only for security, if for no other reason than that only freedom can make security secure.”

Karl Popper book The Open Society and Its Enemies

Vol. 2, Ch. 21 "An Evaluation of the Prophecy"
The Open Society and Its Enemies (1945)

“SPAN ID=What_we_should_do> What we should do, I suggest, is to give up the idea of ultimate sources of knowledge, and admit that all knowledge is human; that it is mixed with our errors, our prejudices, our dreams, and our hopes; that all we can do is to grope for truth even though it be beyond our reach. We may admit that our groping is often inspired, but we must be on our guard against the belief, however deeply felt, that our inspiration carries any authority, divine or otherwise. If we thus admit that there is no authority beyond the reach of criticism to be found within the whole province of our knowledge, however far it may have penetrated into the unknown, then we can retain, without danger, the idea that truth is beyond human authority. And we must retain it. For without this idea there can be no objective standards of inquiry; no criticism of our conjectures; no groping for the unknown; no quest for knowledge.

Karl Popper

Introduction "On The Sources of Knowledge and of Ignorance" Section XVII, p. 30 Variant translation: I believe it is worthwhile trying to discover more about the world, even if this only teaches us how little we know. It might do us good to remember from time to time that, while differing widely in the various little bits we know, in our infinite ignorance we are all equal.
If we thus admit that there is no authority beyond the reach of criticism to be found within the whole province of our knowledge, however far we may have penetrated into the unknown, then we can retain, without risk of dogmatism, the idea that truth itself is beyond all human authority. Indeed, we are not only able to retain this idea, we must retain it. For without it there can be no objective standards of scientific inquiry, no criticism of our conjectured solutions, no groping for the unknown, and no quest for knowledge.
Conjectures and Refutations: The Growth of Scientific Knowledge (1963)

“As for Adler, I was much impressed by a personal experience. Once, in 1919, I reported to him a case which to me did not seem particularly Adlerian, but which he found no difficulty in analyzing in terms of his theory of inferiority feelings, although he had not even seen the child. Slightly shocked, I asked him how he could be so sure. "Because of my thousandfold experience," he replied; whereupon I could not help saying: "And with this new case, I suppose, your experience has become thousand-and-one-fold."”

Karl Popper

Conjectures and Refutations: The Growth of Scientific Knowledge (1963)

“We may become the makers of our fate when we have ceased to pose as its prophets.”

Karl Popper book The Open Society and Its Enemies

Introduction
The Open Society and Its Enemies (1945)

“To be ignorant of the past is to remain a child.”

Karl Popper

Cicero
Misattributed

“It seems to me that I may be living too long. Indeed: my nearest relations have all died, and so have some of my best friends, and even some of my best pupils. However, I do not have a reason to complain. I am grateful and happy to be alive, and still be able to continue with my work, if only just. My work seems to me more important than ever.”

Karl Popper

As quoted in "At 90, and Still Dynamic : Revisiting Sir Karl Popper and Attending His Birthday Party" by Eugene Yue-Ching Ho, in Intellectus 23 (Jul-Sep 1992) http://www.eeng.dcu.ie/~tkpw/hk-ies/n23a/

“It seems to me certain that more people are killed out of righteous stupidity than out of wickedness.”

Karl Popper

Source: Conjectures and Refutations: The Growth of Scientific Knowledge (1963), p. 368

“I think so badly of philosophy that I don't like to talk about it. … I do not want to say anything bad about my dear colleagues, but the profession of teacher of philosophy is a ridiculous one. We don't need a thousand of trained, and badly trained, philosophers — it is very silly. Actually most of them have nothing to say.”

Karl Popper

As quoted in "At 90, and Still Dynamic : Revisiting Sir Karl Popper and Attending His Birthday Party" by Eugene Yue-Ching Ho, in Intellectus 23 (Jul-Sep 1992)

“The deepest, the only theme of human history, compared to which all others are of subordinate importance, is the conflict of skepticism with faith.”

Karl Popper

Johann Wolfgang von Goethe in "Israel in the Desert" (1819)
Misattributed

“No rational argument will have a rational effect on a man who does not want to adopt a rational attitude.”

Karl Popper book The Open Society and Its Enemies

Vol. 2, Ch. 24 "Oracular Philosophy and the Revolt against Reason"
The Open Society and Its Enemies (1945)

“… The answer to this problem is: as implied by Hume, we certainly are not justified in reasoning from an instance to the truth of the corresponding law. But to this negative result a second result, equally negative, may be added: we are justified in reasoning from a counterinstance to the falsity of the corresponding universal law (that is, of any law of which it is a counterinstance). Or in other words, from a purely logical point of view, the acceptance of one counterinstance to 'All swans are white' implies the falsity of the law 'All swans are white' - that law, that is, whose counterinstance we accepted. Induction is logically invalid; but refutation or falsification is a logically valid way of arguing from a single counterinstance to - or, rather, against - the corresponding law. This shows that I continue to agree with Hume's negative logical result; but I extend it. This logical situation is completely independent of any question of whether we would, in practice, accept a single counterinstance - for example, a solitary black swan - in refutation of a so far highly successful law. I do not suggest that we would necessarily be so easily satisfied; we might well suspect that the black specimen before us was not a swan.”

Karl Popper book The Logic of Scientific Discovery

Source: The Logic of Scientific Discovery (1934), Ch. 1 "A Survey of Some Fundamental Problems", Section I: The Problem of Induction http://dieoff.org/page126.htm p. 27

“Science may be described as the art of systematic over-simplification — the art of discerning what we may with advantage omit.”

Karl Popper book The Open Universe

The Open Universe : An Argument for Indeterminism (1992), p. 44

“Before we as individuals are even conscious of our existence we have been profoundly influenced for a considerable time (since before birth) by our relationship to other individuals who have complicated histories, and are members of a society which has an infinitely more complicated and longer history than they do (and are members of it at a particular time and place in that history); and by the time we are able to make conscious choices we are already making use of categories in a language which has reached a particular degree of development through the lives of countless generations of human beings before us.... We are social creatures to the inmost centre of our being. The notion that one can begin anything at all from scratch, free from the past, or unindebted to others, could not conceivably be more wrong.”

Karl Popper

As quoted in Popper (1973) by Bryan Magee

“Piecemeal social engineering resembles physical engineering in regarding the ends as beyond the province of technology.”

Karl Popper book The Poverty of Historicism

All that technology may say about ends is whether they are compatible with each other or realizable.
The Poverty of Historicism (1957) Ch. 22 The Unholy Alliance with Utopianism

“If the many, the specialists, gain the day, it will be the end of science as we know it - of great science. It will be a spiritual catastrophe comparable in its consequences to nuclear armament.”

Karl Popper

K. Popper, The Myth of the Framework, London: Routledge. As quoted in The Cambridge Companion to Karl Popper https://books.google.it/Brooks?id=ha6yDAAQBAJ&of=PA173 (2016) by J. Shearmur, G. Stokes

“Scientists try to eliminate their false theories, they try to let them die in their stead. The believer—whether animal or man—perishes with his false beliefs.”

Karl Popper

Source: Epistemology Without A Knowing Subject (1967)

“...non-reproducible single occurrences are of no significance to science.”

Karl Popper book The Logic of Scientific Discovery

Source: The Logic of Scientific Discovery (1934), Ch. 4 "Falsifiability", Section XXII: Falsifiability and Falsification. p. 66.

“Besides, we should never attempt to balance anybody's misery against somebody else's happiness.”

Karl Popper book Conjectures and Refutations

Source: Conjectures and Refutations: The Growth of Scientific Knowledge (1963), pp. 486-487

“Do not allow your dreams of a beautiful world to lure you away from the claims of men who suffer here and now.”

Karl Popper book Conjectures and Refutations

Source: Conjectures and Refutations: The Growth of Scientific Knowledge (1963), p. 485

“Ignorance is not a simple lack of knowledge but an active aversion to knowledge, the refusal to know, issuing from cowardice, pride or laziness of mind.”

Karl Popper

Principle attributed to Popper by Ryszard Kapiscinski in New York Times obituary, 1995.
Misattributed
Source: https://www.nytimes.com/1995/01/01/magazine/lives-well-lived-karl-popper-the-philosopher-as-giantslayer.html