our minds, beyond which they can neither delay nor haften. §. 19. The reafon I have for this odd conjecture, is from obferving that in the impreffions made upon any of our fenfes, we can but to a certain degree perceive any fucceffion; which, if exceeding quick, the fenfe of fucceffion is loft, even in cafes where it is evident that there is a real fucceffion. Let a cannon-bullet pass through a room, and in its way take with it any limb, or fleshy parts of a man; it is as clear as any demonftration can be, that it muft ftrike fucceffively the two fides of the room. It is alfo evident, that it muft touch one part of the flesh firft, and another after, and fo in fucceffion: And yet I believe no-body, who ever felt the pain of fuch a fhot, or heard the blow against the two diftant walls, could perceive any fucceffion either in the pain or found of fo swift a ftroke. Such a part of duration as this, wherein we perceive no fucceffion, is that which we call an instant, and is that which takes up the time of only one idea in our minds, without the fucceffion of another, wherein therefore we perceive no fucceffion at all. §. II. This alfo happens, where the motion is fo flow, as not to fupply a conftant train of fresh ideas to the fenfes, as faft as the mind is capable of receiving new ones into it; and fo other ideas of our own thoughts, having room to come into our minds, between thofe offered to our fenfes by the moving body, there the fense of motion is loft; and the body, though it really moves, yet not changing perceivable diftance with fome other bodies, as faft as the ideas of our own minds do naturally follow one another in train, the thing feems to ftand ftill, as is evident in the hands of clocks and fhadows of fun-dials, and other constant but flow motions; where, though after certain intervals, we perceive by the change of diftance that it it hath moved, yet the motion itfelf we perceive not. §. 12. So that to me it feems, that the conftant and regular fucceflion of ideas in a waking man is, as it were, the measure and ftandard of all other fucceffions: whereof This train the measure of other fuc effions. if any one either exceeds the pace of our ideas, as where two founds or pains, &c. take up in their fucceffion the duration of but one idea, or else where any motion or fucceffion is fo flow, as that it keeps not pace with the ideas in our minds, or the quickness in which they take their turns; as when any one or more ideas, in their ordinary courfe, come into our mind, between those which are offered to the fight by the different perceptible distances of a body in motion, or between founds or smells following one another; there also the fense of a conftant continued fucceffion is loft, and we perceive it not but with certain gaps of reft between. The mind cannot fix long on one invariable idea. §. 13. If it be fo that the ideas of our minds, whilft we have any there, do conftantly change and fhift in a continual fucceffion, it would be impoffible, may any one fay, for a man to think long of any one thing. By which, if it be meant, that a man may have one felf-fame fingle idea a long time alone in his mind, without any variation at all, I think, in matter of fact, it is not poffible; for which (not knowing how the ideas of our minds are framed, of what materials they are made, whence they have their light, and how they come to make their appearances) I can give no other reafon but experience: And I would have any one try whether he can keep one unvaried fingle idea in his mind, without any other, for any confiderable time together. . 14. For trial, let him take any figure, any degree of light or whiteness, or what other he pleases; and he will, I fuppofe, find it difficult to keep all other ideas out of his mind: But that fome, either of another kind, or various confiderations of that idea (each of which confiderations is a new idea) will conftantly fucceed one another in his thoughts, let him be as wary as he can. S. 15. All that is in a man's power in this cafe, I think, is only to mind and obferve what the ideas are that take their turns in his understanding; or else to direct the fort, and call in fuch as he hath a defire or ufe of: but hinder the conftant fucceffion of fresh ones, I think, he cannot, though he may commonly choose whether he will heedfully obferve and confider them. §. 16. Ideas, however made, 1 include no sense of mo tion. §. 16. Whether these feveral ideas in a man's mind be made by certain motions, I will not here difpute: but this I am fure, that they include no idea of motion in their appearance; and if a man had not the idea of motion otherwife, I think he would have none at all: which is enough to my prefent purpofe, and fufficiently fhows, that the notice we take of the ideas of our own minds, appearing there one after another, is that which gives us the idea of fucceffion and duration, without which we fhould have no fuch ideas at all. It is not then motion, but the conftant train of ideas in our minds, whilft we are waking, that furnishes us with the idea of duration: whereof motion no otherwise gives us any perception, than as it caufes in our minds a conftant fucceffion of ideas, as I have before showed : And we have as clear an idea of fucceffion and duration, by the train of other ideas fucceeding one another in our minds, without the idea of any motion, as by the train of ideas caufed by the uninterrupted fenfible change of distance between two bodies, which we have from motion; and therefore we should as well have the idea of duration, were there no sense of motion at all. §. 17. Having thus got the idea of duration, the next thing natural for the mind to do, is to get fome measure of this common duration, whereby it might judge of its different lengths, and confider the diftinct order wherein feveral things exift, without which a great part of our knowledge would be confufed, and a great part of history be rendered very useless. This confideration of duration, as fet out by certain periods, and marked by certain measures or epochs, is that, I think, which moft properly we call time. §. 18. In the measuring of extenfion, there is nothing more required but the application of the ftandard or measure we make ufe of to the thing, of whofe extenfion we would be informed. But in the measuring of duration, this cannot be done, because no two different parts of fucceffion Time is du ration set out by measures. fure of time A good mea muft divide its whole duration into equal periods. can be put together together to measure one another; and nothing being a measure of duration but duration, as nothing is of extenfion but extenfion, we cannot keep by us any standing unvarying measure of duration, which confifts in a conftant fleeting fucceffion, as we can of certain lengths of extenfion, as inches, fect, yards, &c. marked out in permanent parcels of matter. Nothing then could ferve well for a convenient measure 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 diftinguifhed, or confidered as diftinguished and meafured by fuch periods, come not fo properly under the notion of time, as appears by fuch phrases as thefe, viz. before all time, and when time fhall be no more. The revolutions 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 measure 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 conftant 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 fpace of an annual revolution, it had fenfibly increafed in brightnefs and heat, and fo decreased again; would not such regular appearances ferve to measure out the diftances of duration to all that could obferve it, as well without as with motion? For if the appearances were conftant, univerfally obfervable, and in equidiftant periods, they would ferve mankind for measure of time as well, were the motion away. §. 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, But not by their motion, but periodical appear ances. as the motions of the fun and in effect we fee, that fome people in America counted their years by the coming of certain birds amongst them at their certain feasons, and leaving them at others. For a fit of an ague, the fenfe of hunger or thirst, a fmell or a taste, or any other idea returning conftantly at equidiftant periods, and making itself univerfally be taken notice of, would not fail to measure out the course of fucceffion, and diftinguish the diftances 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 diftinguished his years either by the heat of fummer, or cold of winter; by the smell 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 ufe of, are very irregular? And it adds no fmall 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 |