In the history of physics, (Latin for "I frame no hypotheses", or "I contrive no hypotheses") is a phrase used by Isaac Newton in the essay , which was appended to the second edition of in 1713.
A 1999 translation of the presents Newton's remark as follows:
The 19th-century philosopher of science William Whewell qualified this statement, saying that, "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:<blockquote>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.</blockquote>
Later, Imre Lakatos asserted that such a resignation should not be too rushed.