Cæsar, or many other people, whose years, notwithstanding the motion of the sun, which they pretend to make use of, are very irregular? And it adds no small difficulty to chronology, that the exact lengths of the years that several nations counted by, are hard to be known, they differing very much one from another, and I think I may say all of them from the precise motion of the sun. And if the sun moved from the creation to the flood constantly in the equator, and so equally dispersed its light and heat to all the habitable parts of the earth, in days all of the same length, without its annual variations to the tropics, as a late ingenious author supposes*; I do not think it very easy to imagine, that (notwithstanding the motion of the sun) men should in the antediluvian world from the beginning, count by years, or measure their time by periods, that had no sensible marks very obvious to distinguish them by.

§. 21. Not two parts duration can be certainly known to be equal.

But perhaps it will be said, without a regular motion, such as of the sun, or some other, how could it ever be known, that such periods were equal? To which I answer, the equality of any other returning appearances might be known by the same way that that of days was known, or presumed to be so at first, which was only by judging of them by the train of ideas which had passed in men's minds in the intervals, by which train of ideas discovering inequality in the natural days, but none in the artificial days, the artificial days, or spa were guessed to be equal? which was sufficient to make them serve for a measure; though exacter search has since discovered inequality in the diurnal revolutions of the sun, and we know not whether the annual also be not unequal. These yet, by their presumed and apparent equality, serve 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 distinguish betwixt duration itself, and the measures we make use of to judge of its length. Duration in itself is to be considered as going on in one constant, equal, uniform course: but none of the measures of it, which we make use of, can be known to do so; nor can we be assured, that their assigned parts or

* Dr. Burnet's Theory of the Earth.

periods are equal in duration one to another; for two successive lengths of duration, however measured, can never be demonstrated to be equal. The motion of the sun, which the world used so long, and so confidently, for an exact measure of duration, has, as I said, been found in its several parts unequal: and though men have of late made use of a pendulum, as a more steady and regular motion, than that of the sun, (or, to speak more truly) of the earth; yet if any one should be asked how he certainly knows that the two successive swings of a pendulum are equal, it would be very hard to satisfy him, that they are infallibly so: since we cannot be sure that the cause of that motion, which is unknown to us, shall always operate equally; and we are sure that the medium in which the pendulum moves, is not constantly the same: Either of which varying, may alter the equali ty of such periods, and thereby destroy the certainty and ex ctness 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 canuot any of them be demonstrated to be exact. Since then no two portions of succession can be brought together, it is impossible ever certainly to know their equality. All that we can do for a measure of time is to take such as have continual successive appearances at seemingly equidistant periods; of which seeming equality we have no other neasure, but such as the train of our own ideas have lodged in our memories, with the concurrence of other probable reasons to persuade us of their equality.

§. 22. Time not the measure of motion.

One thing seems strange to me, that whilst all men manifestly measured time by the motion of he great and vi◄ sible bodies of the world, time yet should be defined to be the "measure of motion;" whereas it is obvious to every one who reflects ever so little on it, that to measure motion, space is as necessary to be considered as time: and those who look a little farther, will find also the bulk of the thing moved necessary to be taken into the computation, by any one who will estimate or measure motion, so as to judge right of it. Nor indeed does motion any otherwise conduce to the measuring of duration, than as it constantly brings about the return of certain sensible ideas, in seeming equidistant periods. For if the motion

of the sun were as unequal as of a ship driven by unsteady winds, sometimes very slow, and at others irregularly very swift; or if being constantly equally swift, it yet was not circular, and produced not the same appearances, it would not at all help us to measure time, any more than the seeming unequal motion of a comet does. §. 23. Minutes, hours, days, and years, not necessary measures of duration.

Minutes, hours, days, and years, are then no more necessary to time or duration, than inches, feet, yards, and miles, marked out in any matter, are to extension: For though we in this part of the universe, by the constant use of them, as of periods set out by the revolutions of the sun, or as known parts of such periods, have fixed the ideas of such lengths of duration in our minds, which we apply to all parts of time, whose lengths we would consider; 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 something analogous to them there must be. For without some regular periodical returns, we could not measure ourselves, or signify to others, the length of any duration, though at the same time the world were as full of motion as it is now, but no part of it disposed into regular and apparently equidistant revolutions. But the different

measures that may be made use 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 standards of a foot and a cubit alter the notion of extension to those who make use of those different measures.

§. 24. Our measure of time applicable to duration before

time.

The mind having once got such a measure of time as the annual revolution of the sun, can apply that measure to duration, wherein that measure itself did not exist, and with which, in the reality of its being, it had nothing to do: for should one say, that Abraham was born in the two thousand seven hundred and twelfth year of the Julian period, it is altogether as intelligible, as reckoning from the beginning of the world, though there were so far back no motion of the sun, nor any motion at all. though the Julian period be supposed to begin several

For

hundred years before there were really either days, nights, or years marked out by any revolutions of the sun; yet we reckon as right, and thereby measure durations as well as if really at that time the sun had existed, and kept the same ordinary motion it doth now. The idea of duration equal to an annual revolution of the sun, is as easily applicable in our thoughts to duration,, where no sun or motion was, as the idea of a foot or yard, taken from bodies here, can be applied in our thoughts to distances beyond the confines of the world, where are no bodies at all.

§. 25.

For supposing it were five thousand six hundred and thirty-nine miles, or millions of miles, from this place to the remotest body of the universe (for being finite, it must be at a certain distance) as we suppose it to be five thousand six hundred and thirty-nine years from this time to the first existence of any body in the beginning of the world; we can, in our thoughts, apply this measure of a year to duration before the creation, or beyond the duration of bodies or motion, as we can this measure of a mile to space beyond the utmost bodies; and by the one measure duration where there was no motion, as well as by the other measure space in our thoughts, where there is no body.

§. 26.

If it be objected to me here, that in this way of explaining of time, I have begged what I should not, viz. that the world is neither eternal nor infinite; I answer that to my present purpose it is not needful, in this place, to make use of arguments, to evince the world to be finite, both in duration and extension; but it being at least as conceivable as the contrary, I have certainly the liberty to suppose it, as well as any one hath to suppose the contrary and I doubt not but that every one that will go about it, may easily conceive in his mind the beginning of motion, though not of all duration, and so may come to a stop and non ultra in his consideration of motion. So also in his thoughts he may set limits to body, and the extension belonging to it, but not to space where no body is; the utmost bounds of space and duration being beyond the reach of thought, as well as the utmost bounds of number are beyond the largest comprehension of the mind; and all for the same reason, as we shall see in another place.

§. 27. Eternity.

By the same means thereof, and from the same original that we come to have the idea of time, we have also that idea which we call eternity: viz having got the idea · of succession and duration, by reflecting on the train of ou: own ideas, caused in us either by the natural appearances of those ideas coming constantly of themselves into our waking thoughts, or else caused by external objects successively affecting our senses; and having from the revolutions of the sun got the ideas of certain lengths in duration, we can, in our thoughts, add such lengths of duration to one another, as often as we please, and apply them, so added, to durations past or to come: and this we can continue to do on, without bounds or limits, and proceed in infinitum, and apply thus the length of the annual motion of the sun to duration, supposed before the sun's or any other motion had its being; which is no more difficult or absurd, than to apply the notion I have of the moving of a shadow one hour to-day upon the sun-dial to the duration of something last night, v. g. the burning of a candle, which is now absolutely separate from all actual motion: and it is as impossible for the duration of that flame for an hour last night to co-exist with any motion that now is or or ever shall be, as for any part of duration, that was before the beginning of the world, to co-exist with the motion of the sun now. But yet this hinders not, but that haaving the idea of the length of the motion of the shadow on a dial between the marks of two hours, I can as distinctly measure in my thoughts the duration of that candlelight last night, as I can the duration of any thing that does now exist: And it is no more than to think, that bad the sun shone then on the dial, and moved after the same rate it doth now, the shadow on the dial would have passed from one hour-line to another, whilst that flame of the candle lasted.

§. 28.

The notion of an hour, day, or year, being only the idea I have of the length of certain periodical regular motions, neither of which motions do ever all at once exist, but only in the ideas I have of them in my memory derived from my senses or reflection; I can with the same ease, and for the same reason, apply it in my thoughts to duration antecedent to ali manner of motion, as well as to any thing that is but a min ute, or a day, antecedent to the motion