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.
Science may be described as the art of systematic over-simplification.
Our civilization...has not yet fully recovered from the shock of its birth - the transition from the tribal or 'closed society', with its submission to magical forces, to the 'open society' which sets free the critical powers of man.
No rational argument will have a rational effect on a man who does not want to adopt a rational attitude.
Good tests kill flawed theories; we remain alive to guess again.
There is no history of mankind, there are only many histories of all kinds of aspects of human life. And one of these is the history of political power. This is elevated into the history of the world.
Our knowledge can only be finite, while our ignorance must necessarily be infinite.
Science must begin with myths, and with the criticism of myths.
Those who promise us paradise on earth never produced anything but a hell.
We must plan for freedom, and not only for security, if for no other reason than that only freedom can make security secure.
Unlimited tolerance must lead to the disappearance of tolerance. If we extend unlimited tolerance even to those who are intolerant, if we are not prepared to defend a tolerant society against the onslaught of the intolerant, then the tolerant will be destroyed, and tolerance with them We should therefore claim, in the name of tolerance, the right not to tolerate the intolerant. We should claim that any movement preaching intolerance places itself outside the law, and we should consider incitement to intolerance and persecution as criminal, in the same way as we should consider incitement to murder, or to kidnapping, or to the revival of the slave trade, as criminal.
We have become makers of our fate when we have ceased to pose as its prophets.
Piecemeal social engineering resembles physical engineering in regarding the ends as beyond the province of technology.
In so far as a scientific statement speaks about reality, it must be falsifiable; and in so far as it is not falsifiable, it does not speak about reality.
Philosophers should consider the fact that the greatest happiness principle can easily be made an excuse for a benevolent dictatorship. We should replace it by a more modest and more realistic principle the principle that the fight against avoidable misery should be a recognized aim of public policy, while the increase of happiness should be left, in the main, to private initiative.
It is impossible to speak in such a way that you cannot be misunderstood.
More Karl Popper Quotations (Based on Topics)
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Lao Tzu - Friedrich Nietzsche - Francis Bacon - David Hume - Zhuangzi - Robert M. Pirsig - Ludwig Wittgenstein - Charles de Montesquieu - Avicenna - Amartya Sen