What men of science want is only a fair day's wages for more than a fair day's work.

There are some men who are counted great because they represent the actuality of their own age, and mirror it as it is. Such an one was Voltaire, of whom it was epigrammatically said: "he expressed everybody's thoughts better than anyone." But there are other men who attain greatness because they embody the potentiality of their own day and magically reflect the future. They express the thoughts which will be everybody's two or three centuries after them. Such as one was Descartes.

Man's Place in Nature.

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 that there are a great many people in the world who are just as clever as you are. You learn to put your trust, by and by, in an economy and frugality of the exercise of your powers, both moral and intellectual; and you very soon find out, if you have not found it out before, that patience and tenacity of purpose are worth more than twice their weight of cleverness.

Ecclesiasticism in science is only unfaithfulness to truth

The only objections that have occurred to me are, 1st that you have loaded yourself with an unnecessary difficulty in adopting Natura non facit saltum so unreservedly. . . . And 2nd, it is not clear to me why, if continual physical conditions are of so little moment as you suppose, variation should occur at all. However, I must read the book two or three times more before I presume to begin picking holes.

A man who speaks out honestly and fearlessly that which he knows, and that which he believes, will always enlist the good will and the respect, however much he may fail in winning the assent, of his fellow men.