Genuine philosophical problems are always rooted outside philosophy and they die if these roots decay.

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

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.

The defence of democracy must consist in making anti-democratic experiences too costly for those who try them; much more costly than a democratic compromise

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.

Historically speaking all - or very nearly all - scientific theories originate from myths.

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