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, 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.

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

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

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.

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 often asserted that discussion is only possible between people who have a common language and accept common basic assumptions. I think that this is a mistake. All that is needed is a readiness to learn from one's partner in the discussion, which includes a genuine wish to understand what he intends to say. If this readiness is there, the discussion wrighteous stupidityill be the more fruitful the more the partner's backgrounds differ.

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