The moral decisions of others should be treated with respect, as long as such decisions do not conflict with the principle of tolerance.

Plato felt that a complete reconstruction of society's political program was needed.

A theory is just a mathematical model to describe the observations.

The old scientific ideal of episteme - of absolutely certain, demonstrable knowledge - has proved to be an idol. The demand for scientific objectivity makes it inevitable that every scientific statement must remain tentative for ever.

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.

Criticism of my alleged views was widespread and highly successful. I have yet to meet a criticism of my views.

No particular theory may ever be regarded as absolutely certain.... No scientific theory is sacrosanct.