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Prior to the publication of The ''Principia'', the philosophy of motion and change in the universe was largely a theoretical and non-mathematical enterprise. The dominating methodological approach both in the Aristotelian-scholastic and Cartesian natural philosophy, was one in which truths about the natural world were proposed as conjectural hypotheses. The were often deduced fundamental metaphysical principles that were deemed evidently true by human reason [[CiteRef::Janiak (20142016)]][[CiteRef::Lennon and Dea (2014)]]. Influenced by the more experimental and mathematically oriented methodologies of Bacon, Galileo, and Boyle, Newton explicitly rejected the method of hypotheses, and instead demanded that all propositions be deduced from the observed phenomena and then converted into general principles via '''induction''' [[CiteRef::McMullin (2001)]][[CiteRef::Janiak (20142016)]][[CiteRef::Smith (2002)]]. In the second edition of The ''Principia'', Newton states:

Using these principles, Newton was able claimed to derive the have derived his law of universal gravity in the context gravitation using this method as applied to Kepler's laws of his methodplanetary motion. In the Cartesian mosaicnatural philosophy, the centripetal force had already been defined as the agent that pulled the moon towards the Earth, keeping its orbit circular rather than linear. Newton applied rules 1) and 2) to determine that the centripetal force, and the force that compelled objects to move downwards towards the Earth, were merely two different expressions of the same thing. Newton then went on to apply the third rule, and argue that this force, which he called gravity, must be a universal property of all material objects. From here, he went on to argue for the unification of superlunary and sublunary phenomena.[[CiteRef::Harper (2002)|pp. 183-184]]