Hypotheses non fingo


Hypotheses non fingo is a famous phrase used by Isaac Newton in an essay, "General Scholium", which was appended to the second edition of the Principia.
Here is a modern translation of the passage containing this famous remark:
The nineteenth century philosopher of science, William Whewell, qualified this statement, as, he said, "it was by such a use of hypotheses, that both Newton himself and Kepler, on whose discoveries those of Newton were based, made their discoveries". Whewell stated:
What is requisite is, that the hypothesis should be close to the facts, and not connected with them by other arbitrary and untried facts; and that the philosopher should be ready to resign it as soon as the facts refuse to confirm it.

Later, Imre Lakatos would assert that that resignation should not be too rushed.