Even mistaken hypotheses and theories are of use in leading to discoveries. This remark is true in all the sciences. The alchemists founded chemistry by pursuing chimerical problems and theories which are false. In physical science, which is more advanced than biology, we might still cite men of science who make great discoveries by relying on false theories.

Obervation is a passive science, experimentation is an active science.

The minds that rise and become really great are never self-satisfied, but still continue to strive.

But while I accept specialization in the practice, I reject it utterly in the theory of science.

With the aid of these active experimental sciences man becomes an inventor of phenomena, a real foreman of creation; and under this head we cannot set limits to the power that he may gain over nature through future progress of the experimental sciences.

A fact in itself is nothing. It is valuable only for the idea attached to it, or for the proof which it furnishes.

We must keep our freedom of mind, ... and must believe that in nature what is absurd, according to our theories, is not always impossible.