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

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.

Every great advance in natural knowledge has involved the absolute rejection of authority.

The rules of the game are what we call the laws of nature.

The scientific imagination always restrains itself within the limits of probability.

It is one of the most saddening things in life that, try as we may, we can never be certain of making people happy, whereas we can almost always be certain of making them unhappy.

The great tragedy of science - the slaying of a beautiful hypothesis by an ugly fact.