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 never know what we are talking about.

The scientific tradition is distinguished from the pre-scientific tradition by having two layers. Like the latter, it passes on its theories; but it also passes on a critical attitude towards them.

I have insisted that we must be tolerant. But I also believe that this tolerance has its limits. We must not trust those anti-humanitarian religions which not only preach destruction but act accordingly. For if we tolerate them, then we become ourselves responsible for for their deeds.

With regards to political enemies Plato had a kill-and-banish principle. ... In interpreting it , modern-day Platonists are clearly disturbed by it, even as they make elaborate attempts to defend Plato.

We are social creatures to the inmost centre of our being. The notion that one can begin anything at all from scratch, free from the past, or unindebted to others, could not conceivably be more wrong.

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.