Top 140 Karl Popper Quotes (2025 Update)
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101. “The use of violence is justified only under a tyranny which makes reforms without violence impossible, and should have only one aim, that is, to bring about a state of affairs which makes reforms without violence possible.”

— Karl Popper

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

— Karl Popper

103. “It is not possible to write clearly enough to avoid being misrepresented by people who are sufficiently determined to do so.”

— Karl Popper

104. “The war of ideas is a Greek invention. It is one of the most important inventions ever made. Indeed, the possibility of fighting with with words and ideas instead of fighting with swords is the very basis of our civilization, and especially of all its legal and parliamentary institutions.”

— Karl Popper

105. “Our aim as scientists is objective truth; more truth, more interesting truth, more intelligible truth. We cannot reasonably aim at certainty. Once we realize that human knowledge is fallible, we realize also that we can never be completely certain that we have not made a mistake.”

— Karl Popper

106. “The history of science, like the history of all human ideas, is a history of irresponsible dreams, of obstinacy, and of error.”

— Karl Popper

107. “Every ‘good’ scientific theory is a prohibition: it forbids certain things to happen. The more a theory forbids, the better it is.”

— Karl Popper

108. “There is no history of mankind, there is only an indefinite number of histories of all kinds of aspects of human life.”

— Karl Popper

109. “It is the rule which says that the other rules of scientific procedure must be designed in such a way that they do not protect any statement in science against falsification.”

— Karl Popper

110. “For nothing could be better than living a modest, simple, and free life in an egalitarian society. It took some time before I recognized this as no more than a beautiful dream; that freedom is more important than equality; that the attempt to realize equality endangers freedom; and that, if freedom is lost, there will not even be equality among the unfree.”

— Karl Popper

111. “Plato felt that a complete reconstruction of society’s political program was needed.”

— Karl Popper

112. “Reason like science, grows by way of mutual criticism; the only possible way of planning its growth is to develop those institutions that safeguard. the freedom of thought.”

— Karl Popper

113. “I hold that he who teaches that not reason but love should rule opens up the way for those who rule by hate.”

— Karl Popper

114. “It is a myth that the success of science in our time is mainly due to the huge amounts of money that have been spent on big machines. What really makes science grow is new ideas, including false ideas.”

— Karl Popper

115. “I have learned more from Hayek than from any other living thinker, except perhaps Alfred Tarski – but not even excepting Russell.”

— Karl Popper

116. “What we call nowadays totalitarianism belongs to a tradition which is just as old or just as young as our civilization itself.”

— Karl Popper

117. “The scientific tradition is distinguished from the pre-scientific tradition by having two layers. Like the latter, it passes on its theories; but it also passes on a critical attitude towards them.”

— Karl Popper

118. “We have the right not to tolerate the intolerant. We should tolerate even them whenever we can do so without running a great risk; but the risk may become so great that we cannot allow ourselves the luxury.”

— Karl Popper

119. “Philosophy is a necessary activity because we, all of us, take a great number of things for granted, and many of these assumptions are of a philosophical character; we act on them in private life, in politics, in our work, and in every other sphere of our lives – but while some of these assumptions are no doubt true, it is likely, that more are false and some are harmful. So the critical examination of our presuppositions – which is a philosophical activity – is morally as well as intellectually important.”

— Karl Popper

120. “All we can do is search for the falsity content in our best theory.”

— Karl Popper

121. “The way of science is paved with discarded theories which were once declared self-evident;.”

— Karl Popper

122. “It must be possible for an empirical system to be refuted by experience.”

— Karl Popper

123. “The essential feature of dualist-interactionism is that the mind and brain are independent entities... and that they interact by quantum physics.”

— Karl Popper

124. “Instead of the greatest happiness for the greatest number, one should demand, more modestly, the least amount of avoidable suffering for all; and further, that unavoidable suffering – such as hunger in times of an unavoidable shortage of food – should be distributed as equally as possible.”

— Karl Popper

125. “Science is most significant as one of the greatest spiritual adventures that man has yet known.”

— Karl Popper

126. “I wish to make it clear that ‘history’ in the sense in which most people speak of it simply does not exist; and this is at least one reason why I say that it has no meaning.”

— Karl Popper

127. “The initial stage, the act of conceiving or inventing a theory, seems to me neither to call for logical analysis nor to be susceptible of it.”

— Karl Popper

128. “The quest for precision is analogous to the quest for certainty, and both should be abandoned.”

— Karl Popper

129. “We must regard all laws or theories as hypothetical or conjectural; that is, as guesses.”

— Karl Popper

130. “Criticism, I said, is an attempt to find the weak spots in a theory, and these, as a rule, can be found only in the more remote logical consequences which can be derived from it. It is here that purely logical reasoning plays an important part in science.”

— Karl Popper

131. “Again, we cannot search the whole world in order to make sure that nothing exists which the law forbids. Nevertheless, both kinds of strict statements, strictly existential and strictly universal, are in principle empirically decidable, each, however, in one way only: they are unilaterally decidable. Whenever it is found that something exists here or there, a strictly existential statement may thereby be verified, or a universal one falsified.”

— Karl Popper

132. “This is why the conflict between rationalism and irrationalism has become the most important intellectual, and perhaps even moral, issue of our time.”

— Karl Popper

133. “The simple truth is that truth is hard to come by, and that once found may easily be lost again.”

— Karl Popper

134. “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.”

— Karl Popper

135. “The fundamental thing about human languages is that they can and should be used to describe something; and this something is, somehow, the world. To be constantly and almost exclusively interested in the medium – in spectacle-cleaning – is a result of a philosophical mistake.”

— Karl Popper

136. “Contrary to the outstanding work of art, outstanding theory is susceptible to improvements.”

— Karl Popper

137. “Marxism is only an episode – one of the many mistakes we have made in the perennial and dangerous struggle for building a better and freer world.”

— Karl Popper

138. “There is no law of progress, and everything will depend on ourselves. But the actual situation is briefly and fairly summed up by Parkes36 in one sentence: ‘Low wages, long hours, and child labour have been characteristic of capitalism not, as Marx predicted, in its old age, but in its infancy.”

— Karl Popper

139. “Denying realism amounts to megalomania.”

— Karl Popper

140. “Is it within the power of any social science to make sweeping historical prophecies? Can we expect to get more than the irresponsible reply of the soothsayer if we ask a man what the future has in store for mankind?”

— Karl Popper

141. “The ‘conspiracy theory of society’ is a typical result of a secularization of a religious superstition. The belief in the Homeric gods whose conspiracies explain the history of the Trojan War is gone. The gods are abandoned. But their place is filled by powerful men or groups – sinister pressure groups whose wickedness is responsible for all the evils we suffer from – such as the Learned Elders of Zion, or the monopolists, or the capitalists, or the imperialists.”

— Karl Popper

142. “The point is that, whenever we propose a solution to a problem, we ought to try as hard as we can to overthrow out solution, rather than defend it. Few of us, unfortunately, praise this precept; but other people, fortunately, will supply the criticism for us if we fail to supply it ourselves. Yet criticism will be fruitful only if we state our problem as clearly as we can and put our solution in a sufficiently definite form – a form in which it can be critically discussed.”

— Karl Popper

143. “Science can be viewed from various standpoints, not only from that of epistemology; for example, we can look at it as a biological or as a sociological phenomenon. As such it might be described as a tool, or an instrument, comparable perhaps to some of our industrial machinery. Science may be described as a means of production – as the last word in ’roundabout production.”

— Karl Popper

144. “I wish to apologize to the Kantians for mentioning them in the same breath as the Hegelians.”

— Karl Popper

145. “The question of the acceptance of theories should, I propose, be demoted to the status of a minor problem. For science may be regarded as a growing system of problems, rather than as a system of beliefs. And for a system of problems, the tentative acceptance of a theory or a conjecture means hardly more than that it is considered worthy of further criticism.”

— Karl Popper