We must protect the right of our opponents to speak because we must hear what they have to say.

The radical novelty of modern science lies precisely in the rejection of the belief... that the forces which move the stars and atoms are contingent upon the preferences of the human heart.

True opinions can prevail only if the facts to which they refer are known; if they are not known, false ideas are just as effective as true ones, if not a little more effective.

What we call a democratic society might be defined for certain purposes as one in which the majority is always prepared to put down a revolutionary minority.

The central drama of our age is how the Western nations and the Asian peoples are to find a tolerable basis of co-existence.

There is no arguing with the pretenders to a divine knowledge and to a divine mission. They are possessed with the sin of pride, they have yielded to the perennial temptation.

What each man does is based not on direct and certain knowledge, but on pictures made by himself or given to him...