The moral decisions of others should be treated with respect, as long as such decisions do not conflict with the principle of tolerance.
I have learned more from Hayek than from any other living thinker, except perhaps Alfred Tarski – but not even excepting Russell.
The open society is one in which men have learned to be to some extent critical of taboos, and to base decisions on the authority of their own intelligence.
We must plan for freedom, and not only for security, if for no other reason than only freedom can make security more secure.
It is wrong to think that belief in freedom always leads to victory; we must always be prepared for it to lead to defeat. If we choose freedom, then we must be prepared to perish along with it.
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.
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.
I have spoken to Einstein and he admitted to me that his theory was in fact no different from the one of Parmenides.
A theory that explains everything, explains nothing.
It must be possible for an empirical system to be refuted by experience.
We never know what we are talking about.
There is no history of mankind, there is only an indefinite number of histories of all kinds of aspects of human life.
But some of these theories are so bold that they can clash with reality: they are the testable theories of science. And when they clash, then we know that there is a reality; something that can inform us that our ideas are mistaken.
There can be no ultimate statements science: there can be no statements in science which can not be tested, and therefore none which cannot in principle be refuted, by falsifying some of the conclusions which can be deduced from them.
The history of science, like the history of all human ideas, is a history of irresponsible dreams, of obstinacy, and of error.
But it is certainly not possible to insist on one hand that the formalism is complete and to insist on the other hand that its application to ‘the actual’ actually demands a step which cannot be derived from it.
Science is perhaps the only human activity in which errors are systematically criticized and, in time, corrected.
Genuine philosophical problems are always rooted outside philosophy and they die if these roots decay.
Thus science must begin with myths, and with the criticism of myths; neither with the collection of observations, nor with the invention of experiments, but with the critical discussion of myths, and of magical techniques and practices.
Propose theories which can be criticized. Think about possible decisive falsifying experiments-crucial experiments. But do not give up your theories too easily-not, at any rate, before you have critically examined your criticism.