For every man the world is as fresh as it was at the first day, and as full of untold novelties for him who has the eyes to see them.

Logical consequences are the scarecrows of fools and the beacons of wise men.

In the world of letters, learning and knowledge are one, and books are the source of both; whereas in science, as in life, learning and knowledge are distinct, and the study of things, and not of books, is the source of the latter.

Unfortunately, it is much easier to shut one's eyes to good than to evil. Pain and sorrow knock at our doors more loudly than pleasure and happiness; and the prints of their heavy footsteps are less easily effaced.

In scientific work, those who refuse to go beyond fact rarely get as far as fact.

Though under-instruction is a bad thing, it is not impossible that over-instruction may be worse.

I have always been, am, and propose to remain a mere scholar. All that I have ever proposed to myself is to say, this and this I have learned; thus and thus have I learned it; go thou and learn better; but do not thrust on my shoulders the responsibility for your own laziness if you elect to take, on my authority, conclusions the value of which you ought to have tested for yourself.