I frame no hypotheses; for whatever is not deduced from the phenomena is to be called an hypothesis; and hypotheses, whether metaphysical or physical, whether of occult qualities or mechanical, have no place in experimental philosophy.

Newton’s “I frame no hypotheses” remark appears in the “General Scholium” appended to later editions of the Principia, where he responded to critics and clarified his method after the book’s initial reception. In the wake of debates about the cause of gravity—especially demands that he supply a mechanical explanation—Newton insisted that his task in “experimental philosophy” was to infer general laws from observed phenomena and to avoid speculative causal stories not warranted by evidence. The statement is thus part methodological manifesto, part polemical defense of the Principia’s approach to natural philosophy in the early 18th century.

Newton draws a sharp boundary between empirically grounded inference and conjecture. He argues that explanations not demonstrably derived from observed phenomena count as “hypotheses,” and that such hypotheses—whether metaphysical, occult, or mechanistic—should not be treated as established knowledge within experimental science. The point is not that scientists may never propose conjectures, but that conjectures must not be confused with demonstrated results. In context, Newton is defending the legitimacy of describing gravitational effects and formulating universal laws without claiming a proven account of gravity’s underlying mechanism, emphasizing disciplined inference over speculative system-building.

“Hypotheses non fingo.” (Latin formulation commonly cited from the General Scholium.)