together to meafure one another: and nothing being a meafure of duration but duration, as nothing is of extenfion but extenfion, we cannot keep by us any standing unvarying meafure of duration, which contifis in a conftant fleeting fucceffion, as we can of certain lengths of extenfion, as inches, feet, yards, &c. marked out-in permanent parcels of matter. Nothing then could ferve well for a convenient meafure of time, but what has divided the whole length of its duration into apparently equal portions, by conftantly repeated periods. What portions of duration are not diftinguished, or confidered as diftinguifhed and measured by fuch periods, come not fo properly under the notion of time, as appears by fuch phrafes as thefe, viz. before all time, and when time fhall be no more. The revolu tions of the fun and moon, the propereft measures of time. §. 19. The diurnal and annual revolutions of the fun, as having been, from the beginning of nature, conftant, regular, and univerfally obfervable by all mankind, and fuppofed equal to one another, have been with reafon made ufe of for the measure of duration. But the diftinction of days and years having depended on the motion of the fun, it has brought this mistake with it, that it has been thought that motion and duration were the meafure one of another: for men, in the measuring of the length of time, having been accustomed to the ideas of minutes, hours, days, months, years, &c. which they found themfelves upon any mention of time or duration prefently to think on, all which portions of time were meafured out by the motion of thofe heavenly bodies: they were apt to confound time and motion, or at leaft to think that they had a neceffary connexion one with another: whereas any conftant periodical appearance, or alteration of ideas in feemingly equidiftant fpaces of duration, if constant and univerfally obfervable, would have as well diftinguished the intervals of time, as thofe that have been made ufe of. For fuppofing the fun, which fome have taken to be a fire, had been lighted up at the fame diftance of time that it now every day comes about to the fame meridian, and then gone out again about about twelve hours after, and that in the space of an annual revolution, it had sensibly increased in brightnefs and heat, and fo decreased again; would not such regular appearances ferve to measure out the distances of duration to all that could obferve it, as well without as with motion? For if the appearances were constant, univerfally obfervable, and in equidiftant periods, they would ferve mankind for meafure of time as well, were the motion away. But not by their motion, but periodical appear ances. §. 20. For the freezing of water, or the blowing of a plant, returning at equidiftant periods in all parts of the earth, woud as well ferve men to reckon their years by, as the motions of the fun and in effect we fee, that some people in America counted their years by the coming of certain birds amongst them at their certain feafons, and leaving them at others. For a fit of an ague, the fenfe of hunger or thirft, a fmell or a taste, or any other idea returning constantly at equidistant periods, and making itself univerfally be taken notice of, would not fail to measure out the course of fucceffion, and diftinguish the distances of time. Thus we fee that men born blind count time well enough by years, whofe revolutions yet they cannot diftinguish by motions, that they perceive not: and I afk whether a blind man, who diftinguifhed his years either by the heat of fummer, or cold of winter; by the fmell of any flower of the fpring, or tafte of any fruit of the autumn; would not have a better measure of time than the Romans had before the reformation of their calendar by Julius Cæfar, or many other people, whofe years, notwithstanding the motion of the fun, which they pretend to make use of, are very irregular? And it adds no small difficuly to chronology, that the exact lengths of the years that feveral nations counted by, are hard to be known, they differing very much one from another, and I think I may fay all of them from the precife motion of the fun. And if the fun moved from the creation to the flood conftantly in the equator, and fo equally difperfed its light and heat to all the habitable parts of the earth, in days all of the fame length, with out its annual variations to the tropicks, as a late ingenious author fuppofes*; I do not think it very eafy to imagine, that (notwithstanding the motion of the fun) men fhould in the antediluvian world from the beginning, count by years, or measure their time by periods, that had no fenfible marks very obvious to diftinguish them by. No two parts §. 21. But perhaps it will be faid, withof duration, out a regular motion, fuch as of the fun, can be cer- or fome other, how could it ever be known tainly known that fuch periods were equal? To which I to be equal. anfwer, the equality of any other returning appearances might be known by the fame way that that of days was known, or prefumed to be fo at firft; which was only by judging of them by the train of ideas which had paffed in men's minds in the intervals: by which train of ideas difcovering inequality in the natural days, but none in the artificial days, the artificial days or unμepa were gueffed to be equal, which was fufficient to make them ferve for a measure: though exacter fearch has fince difcovered inequality in the diurnal revolutions of the fun, and we know not whether the annual alfo be not unequal. Thefe, yet, by their prefumed and apparent equality, ferve as well to reckon time by (though not to measure the parts of duration exactly) as if they could be proved to be exactly equal. We must therefore carefully diftinguish betwixt duration itself, and the measures we make use of to judge of its length. Duration in itfelf is to be confidered as going on in one conftant, equal, uniform courfe but none of the measures of it, which we make ufe of, can be known to do fo; nor can we be affured, that their affigned parts or periods are equal in duration one to another; for two fucceffive lengths of duration, however measured, can never be demonftrated to be equal. The motion of the fun, which the world. ufed fo long and fo confidently for an exact measure of duration, has, as I faid, been found in its feveral parts unequal: And though men have of late made ufe of a * Dr. Burnet's Theory of the Earth. pendulum, pendulum, as a more fteady and regular motion than that of the fun, or (to speak more truly) of the earth; yet if any one fhould be afked how he certainly knows that the two fucceffive fwings of a pendulum are equal, it would be very hard to fatisfy him that they are infallibly fo fince we cannot be fure, that the cause of that motion, which is unknown to us, fhall always operate equally; and we are fure that the medium in which the pendulum moves, is not conftantly the fame: Either of which varying, may alter the equality of fuch periods, and thereby deftroy the certainty and exactnefs of the measure by motion, as well as any other periods of other appearances; the notion of duration still remaining clear, though our measures of it cannot any of them be demonftrated to be exact. Since then no two portions of fucceffion can be brought together, it is impoffible ever certainly to know their equality. All that we can do for a measure of time is to take fuch as have continual fucceffive appearances at feemingly equidiftant periods; of which feeming equality we have no other measure, but fuch as the train of our own ideas have lodged in our memories, with the concurrence of other probable reafons, to perfuade us of their equality. Time not the motion. measure of §. 22. One thing feems ftrange to me, that whilst all men manifeftly meafured time by the motion of the great and vifible bodies of the world, time yet fhould be defined to be the "meafure of motion;" whereas it is obvious to every one who reflects ever fo little on it, that to measure motion, fpace is as neceffary to be confidered as time: and those who look a little farther, will find alfo the bulk of the thing moved neceffary to be taken into the computation, by any one who will estimate or measure motion, fo as to judge right of it. Nor indeed does motion any otherwife conduce to the measuring of duration, than as it conftantly brings about the return of certain fenfible ideas, in feeming equidiftant periods. For if the motion of the fun were as unequal as of a fhip driven by unfteady winds, fometimes very flow, and at others irregularly very swift: or or if being conftantly equally fwift, it yet was not circular, and produced not the fame appearances, it would not at all help us to measure time, any more than the feeming unequal motion of a comet does. Minutes, hours, days, and years, not neceffary meafures of duration. §. 23. Minutes, hours, days, and years, are then no more neceffary to time or duration, than inches, feet, yards, and miles, marked out in any matter, are to extenfion For though we in this part of the univerfe, by the conftant ufe of them, as of periods fet out by the revolutions of the fun, or as known parts of fuch periods, have fixed the ideas of fuch lengths of duration in our minds, which we apply to all parts of time, whofe lengths we would confider; yet there may be other parts of the universe, where they no more use these measures of ours, than in Japan they do our inches, feet, or miles; but yet fomething analagous to them there must be. For without fome regular periodical returns, we could not measure ourfelves, or fignify to others, the length of any duration, though at the fame time the world were as full of motion as it is now, but no part of it difpofed into regular and apparently equidiftant revolutions. But the different measures that may be made ufe of for the account of time, do not at all alter the notion of duration, which is the thing to be measured; no more than the different ftandards of a foot and a cubit alter the notion of extenfion to thofe who make ufe of thofe different measures. Our measure of time applicable to duration before time. §. 24. The mind having once got fuch a measure of time as the annual revolution of the fun, can apply that measure to duration, wherein that measure itself did not exift, and with which, in the reality of its being, it had nothing to do: for fhould one fay, that Abraham was born in the two thousand feven hundred and twelfth year of the Julian period, it is altogether as intelligible, as reckoning from the beginning of the world, though there were fo far back no motion of the fun, nor any motion at all. For though the Julian period be fuppofed to begin feveral hundred years be fore |