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.

Mathematics may be compared to a mill of exquisite workmanship, which grinds your stuff to any degree of fineness.

It does not matter how many tumbles you have in this life, so long as you do not get dirty when you tumble; it is only the people who have to stop to be washed and made clean, who must necessarily lose the race. And I can assure you that there is the greatest practical benefit in making a few failures early in life. You learn that which is of inestimable importance

I doubt the fact, to begin with, but if it be so even, what is this but in grand words asking me to believe a thing because I like it.

I protest that if some great Power would agree to make me always think what is true and do what is right, on condition of being turned into a sort of clock and would up every morning before I got out of bed, I should instantly close with the offer.

Make up your mind to act decidedly and take the consequences. No good is ever done in this world by hesitation.

The facts of variability, of the struggle for existence, of adaptation to conditions, were notorious enough; but none of us had suspected that the road to the heart of the species problem lay through them, until Darwin and Wallace dispelled the darkness.