One cannot demand of a scholar that he show himself a scholar everywhere in society, but the whole tenor of his behavior must none the less betray the thinker, he must always be instructive, his way of judging a thing must even in the smallest matters be such that people can see what it will amount to when, quietly and self-collected, he puts this power to scholarly use.

Some people feel with their heads and think with their hearts.

To do the opposite of something is also a form of imitation, namely an imitation of its opposite.

Do not say hypothesis, and even less theory: say way of thinking.

Perhaps in time the so-called Dark Ages will be thought of as including our own.

The construction of the universe is certainly very much easier to explain than is that of the plant.

Nothing is more conducive to peace of mind than not having any opinion at all.