Opticks (1721, 3rd Edition) — part 18 of 18

As in Mathematicks, fo in Natural Philofo- phy, the Invelligation of difficult Things by the Method of Analyfis, ought ever to precede the Method of Compofition. This Analyfis con- lifts in making Experiments and Obfervations , and in drawing general Concluiions from them •ty Indudion, and admitting of no Objections againll the Conclufions, but fuch as are taken from Experiments, or other certain Truths. For Hypothefes are not to be regarded in ex- perimental Philofophy. And although the ar- guing from Experiments and Obfervations by Indudion be no Demonftration of general Con- clufions; yet it is the belt way of arguing which the Nature of Things admits of, and may be looked upon as fo much the itronger, by how much the Indudion is more general. And if no Exception occur from Phaenomena, theCon- clufion may be pronounced generally. But if at any time afterwards any Exception lliall oc- cur from Experiments, it may then begin to be pronounced with fuch Exceptions as occur. By this way of Analyfis we may proceed from Com- pounds to Ingredients, and from Motions to the Forces producing them -, and in general , from Effeds to their Caufes, and from particu- lar Caufes to more general ones, till the Argu- ment end in the molt general. This is the Me- thod, of Analyfis : And the Synthefis confiils in alTuming the Caufes difcover'd, and eftabliili'd as Principles, and by them explaining the Phae- nomena

[ 38i ]

nomena proceeding from them, and proving the Explanations.

In the two firfl Books of thefe Opticks, i proceeded by this Analyfis to difcover and prove the original Differences of the Rays of Light in refpeft of Refrangibiliry, Reflexibility, and Co- lour, and their alternate Fits of eafy Reflexion and eafy Tranfmiflion , and the Properties of Bodies, both opake and pellucid, on which their Reflexions and Colours depend. And thele Difcoveries being proved, maybe affumed in the Method of Compolition for explaining the Phaenomena arifmg from them: An In- ftance of w^hich Method T gave in the End of the firfl: Book. In this third Book I have only begun the Analyfis of what remains to be dif- cover'd about Light and its Effedts upon the Frame of Nature, hinting feveral things about it , and leaving the Hints to be examin'd and improv'd by the farther Experiments and Ob- fervations of fuch as are inquifitive. And if natural Philofophy in all its Parts, by purfuing this Method, rfiall at length be perfected, the Bounds of Moral Philofophy wdll be alfo enlar- ged. For fo far as we can know by natural Philofophy what is the firft Caufe, what Power he has over us, and what Benefits we receive from him, fo far our Duty tow^ards him, as well as that towards one another, will appear to us by the Light of Nature. And no doubt, if the Worihip of falfe Gods had not blinded the Flea- then, their moral Philofophy would have gone farther than to the four Cardinal Virtues ; and

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inftead of teaching the Tranfmigration of Souls,' and to worfhip the Sun and Moon, and dead Heroes, they would have taught us to worlliip our true Author and Benefaftor, as their An- celtors did under the Government of Noah and his Sons before they corrupted themfelves. •

FINIS.

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