We have no organ at all for knowledge, for truth: we know (or believe or imagine) precisely as much as may be useful in the interest of the human herd, the species: and even what is here called usefulness is in the end only a belief, something imagined and perhaps precisely that most fatal piece of stupidity by which we shall one day perish.

We are not here concerned with hopes or fears, only with truth as far as our reason permits us to discover it.

It is not when truth is dirty, but when it is shallow, that the lover of knowledge is reluctant to step into its waters.

Ignorance more frequently begets confidence than does knowledge: it is those who know little, and not those who know much, who so positively assert that this or that problem will never be solved by science.

If you are out to describe the truth, leave elegance to the tailor.

Every serious scientific worker is painfully conscious ... of being relegated to an ever-narrowing sphere of knowledge.