All the knowledge we have of nature depends upon facts; for without observations and experiments our natural philosophy would only be a science of terms and an unintelligible jargon. But then we must call in Geometry and Arithmetics, to our Assistance, unless we are willing to content ourselves with natural History and conjectural Philosophy. For, as many causes concur in the production of compound effects, we are liable to mistake the predominant cause, unless we can measure the quantity and the effect produced, compare them with, and distinguish them from, each other, to find out the adequate cause of each single effect, and what must be the result of their joint action.

When mons. Descartes's philosophical Romance, by the Elegance of its Style and the plausible Accounts of natural Phænomena, had overthrown the Aristotelian Physics, the World received but little Advantage by the Change: For instead of a few Pedants, who, most of them, being conscious of their Ignorance, concealed it with hard Words and pompous Terms; a new Set of Philosophers started up, whose lazy Disposition easily fell in with a Philosophy, that required no Mathematicks to understand it, and who taking a few Principles for granted, without examining their Reality or Consistence with each other, fancied they could solve all Appearances mechanically by Matter and Motion; and, in their smattering Way, pretended to demonstrate such things, as perhaps Cartesius himself never believed ; his Philosophy (if he bad been in earnest) being unable to stand the test of the Geometry which he was Master of.

It is to Sir Isaac Newton's Application of Geometry to Philosophy, that we owe the routing of this Army of Goths and Vandals in the philosophical World; which he has enriched with more and greater Discoveries, than all the Philosophers that went before him: And has laid such Foundations for future Acquisitions, that even after his Death, his Works still promote natural Knowledge. Before Sir Isaac, we had but wild Guesses at the Cause of the Motion of the Comets and Planets round the Sun', but now he has clearly deduced them from the universal Laws of Attraction (the Existence of which he has proved beyond Contradiction) and has shewn, that the seeming Irregularities of the Moon, which Astronomers were unable to express in Numbers, are but the just Consequences of the Actions of the Sun and Earth upon it, according to their different Positions. His Principles clear up all Difficulties of the various Phænomena of the Tides; and the true Figure of the Earth is now plainly shewn to be a flatted Spheroid higher at the Equator than the Poles, notwithstanding many Assertions and Conjectures to the contrary.

But to return to the Newtonian Philosophy: Tho' its Truth is supported by Mathematicks, yet its Physical Discoveries may be communicated without. The great Mr. Locke was the first who became a Newtonian Philosopher without the help of Geometry; for having asked Mr. Huygens, whether all the mathematical Propositions in Sir Isaac's Principia were true, and being told he might depend upon their Certainty; he took them for granted, and carefully examined the Reasonings and Corollaries drawn from them, became Master of all the Physics, and was fully convinc'd of the great Discoveries contained in that Book.