Every genuine test of a theory is an attempt to falsify it, or to refute it.

The history of science is everywhere speculative. It is a marvelous hiatory. It makes you proud to be a human being.

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

Understanding a theory has, indeed, much in common with understanding a human personality. We may know or understand a man's system of dispositions pretty well; that is to say, we may be able to predict how he would act in a number of different situations. But since there are infinitely many possible situations, of infinite variety, a full understanding of a man's dispositions does not seem to be possible.

It can't happen here is always wrong: a dictatorship can happen anywhere.

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.

If you know that things are bound to happen whatever you do, then you may feel free to give up the fight against them.