Unity of plan everywhere lies hidden under the mask: of diversity of structure-the complex is everywhere evolved out of the simple.

Friendship involves many things but, above all the power of going outside oneself and appreciating what is noble and loving in another.

Skepticism is the highest duty and blind faith the one unpardonable sin.

The best men of the best epochs are simply those who make the fewest blunders and commit the fewest sins.

Time, whose tooth gnaws away everything else, is powerless against truth.

[Scientists] have learned to respect nothing but evidence, and to believe that their highest duty lies in submitting to it however it may jar against their inclinations.

Sit down before fact as a little child, be prepared to give up every conceived notion, follow humbly wherever and whatever abysses nature leads, or you will learn nothing.