If there is anything in the world which I do firmly believe in, it is the universal validity of the law of causation.

I am content with nothing, restless and ambitious... and I despise myself for the vanity, which formed half the stimulus to my exertions. Oh would that I were one of those plodding wise fools who having once set their hand to the plough go on nothing doubting.

The method of scientific investigation is nothing but the expression of the necessary mode of working of the human mind.

To quarrel with the uncertainty that besets us in intellectual affairs would be about as reasonable as to object to live one's life with due thought for the morrow because no man can be sure he will alive an hour hence.

We are prone to see what lies behind our eyes, rather than what apprears before them.

Only a scientific people can survive in a scientific future.

There is no greater mistake than the hasty conclusion that opinions are worthless because they are badly argued.