The course of true anything never does run smooth.

There are two classes [of scientists], those who want to know, and do not care whether others think they know or not, and those who do not much care about knowing, but care very greatly about being reputed as knowing.

Science is being daily more and more personified and anthromorphized into a god. By and by they will say that science took our nature upon him, and sent down his only begotten son, Charles Darwin, or Huxley, into the world so that those who believe in him, &c.; and they will burn people for saying that science, after all, is only an expression for our ignorance of our own ignorance.

Memory and forgetfulness are as life and death to one another. To live is to remember and to remember is to live. To die is to forget and to forget is to die.

If [science] tends to thicken the crust of ice on which, as it were, we are skating, it is all right. If it tries to find, or professes to have found, the solid ground at the bottom of the water it is all wrong. Our business is with the thickening of this crust by extending our knowledge downward from above, as ice gets thicker while the frost lasts; we should not try to freeze upwards from the bottom.

There is no such source of error as the pursuit of absolute truth.

Whereas, to borrow an illustration from mathematics, life was formerly an equation of, say, 100 unknown quantities, it is now one of 99 only, inasmuch as memory and heredity have been shown to be one and the same thing.