Hypotheses non fingo
Hypotheses non fingo (Latin for "I feign no hypotheses," "I frame no hypotheses," or "I contrive no hypotheses") is a famous phrase used by Isaac Newton in an essay, General Scholium, which was appended to the second (1713) edition of the Principia.
Here is a modern translation (published 1999) of the passage containing this famous remark:
I have not as yet been able to discover the reason for these properties of gravity from phenomena, and I do not feign hypotheses. For whatever is not deduced from the phenomena must be called a hypothesis; and hypotheses, whether metaphysical or physical, or based on occult qualities, or mechanical, have no place in experimental philosophy. In this philosophy particular propositions are inferred from the phenomena, and afterwards rendered general by induction.