editor, Administrators
2,020
edits
Changes
no edit summary
=== Newton on Methodology ===
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 to natural philosophy both in the Aristotelian-scholastic and Cartesian mosaic, 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 (2014)]][[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 (2014)]][[CiteRef::Smith (2002)]]. In the second edition of The ''Principia'', Newton states:
<blockquote>I have not as yet been able to deduce from phenomena the reason for these properties of gravity, 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 experimental philosophy, propositions are deduced from the phenomena and are made general by induction. The impenetrability, mobility, and impetus of bodies and the laws of motion and law of gravity have been found by this method. And it is enough that gravity should really exist and should act according to the laws that we have set forth and should suffice for all the motions of the heavenly bodies and of our sea.[[CiteRef::Newton (1999)| p. 276]]</blockquote>
Newton called his method the experimental philosophy, because theories about the behavior of empirical objects can only be refuted via experimental procedures.[[CiteRef::Smith (2002)]] He expressed the core beliefs from which he derived his method in a set of four “rules for the study of natural philosophy,” which he stated in book III of The ''Principia'' as follows:
# In experimental philosophy, propositions gathered from phenomena by induction should be considered either exactly or very nearly true notwithstanding any contrary hypothesis, until yet other phenomena make such propositions either more exact or liable to exceptions.[[CiteRef::Newton (1999)|pp. 794-796]]</blockquote>
Out of these four rules a new, engaged method for conducting science emerged that stood in stark contrast to the previous passive and theoretical Cartesian and Aristotelian-scholastic methods. Propositions are born from natural sources and placed back into the natural world to be tested empirically.[[CiteRef::Smith (2002)]] As the four rules were absorbed into the ensuing mosaic, the calculus became deeply incorporated in the experimental method, as it was used to mathematically calculate empirical predictions from natural laws an empirical prediction, and then evaluate how exactly the prediction matched the observed reality.
Using these principles, Newton was able to derive the law of universal gravity in the context of his method. In the Cartesian mosaic, 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]]