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appearance of any two ideas in our minds, is that we call duration. For whilst we are thinking, or whilst we receive successively several ideas in our minds, we know that we do exist; and so we call the existence, or the continuation of the existence of ourselves, or any thing else, commensurate to the succession of any ideas in our minds, the duration of ourselves, or any such other thing coexistent with our thinking.

9. 4. That we have our notion of succession and duration from this original, viz. from reflection on the train of ideas which we tind to appear one after anothier in our own minds, scems plain to me, in that wc have no perception of duration, but by considering the train of ideas that take their tuns in our understandings. When that succession of ideas ceases, our perception of duration ceases with it; which every one clearly experiments in himself, whilst he sleeps soundly, whether an hour or a day, a month or a year: of which duration of things, while he sleeps or thinks not, he has no perception at all, but it is quite lost to him ; and the moment wherein he leaves off to think, till the moment he begins to think again, seems to him to have no distance. And so I doubt not it would be to a waking man, if it were possible for him to keep only one idea in his mind, without variation and the succession of others. And we see, that one who fixes his thoughts very intently on one thing, so as to take but little porice of the succession of ideas that pass in his mind, whilst he is taken up with that earnest contemplation, lets slip out of his account a good part of that duration, and thinks that time shorter than it is. But if sleep commonly unites the distant parts of duration, it is because during that time we have no sucression of ideas in our minds. For if a man, during his sleep, dreams, and variety of ideas make them selves perceptible in bis mind one after another ; be hath then, during such dreaming, a sense of duration, and of the length of it. By which it is to me very clear, that men derive their ideas of duration from their reflections on the train of the ideas they observe to succeed one another in their own understandings;

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without which observation they can have no notion of
duration, whatever may happen in the world.
§. 5. Indeed, a man having from re-

The idea of flecting on the succession and number of duration aphis own thoughts, got the notion or idea plicable to of duration, he can apply that notion to things whilst

we sleep. things which exist while he does not think ; as he that has got the idea of extension from bodies by his sight or touch, can apply it to distances, where ng body is seen or felt. And therefore though a man håsno perception of the length of duration, which passed whilst he slept or thought not; yet having observed the revolution of days and nights, and found the length of their duration to be in appearance regular and constant, he can, upon the supposition that that revolution has proceeded after the same manner, whilst he was asleep or thought not, as it used to do at other tiines; he can, I say, imagine and make allowance for the length of duration, whilst he slept. But if Adam and Eve (when they were alone in the world) instead of their ordinary night's sleep, had passed the whole twenty-four hours in one continued sleep, the duration of that twentyfour hours had been irrecoverably lost to them, and been for ever left out of their account of time.

§. 6. Thus by reflecting on the appear. The idea of ing of various ideas one after another in succession our understandings, we get the notion of not from succession; which, if any one would think morion. we did rather get from our observation of motion by our senses, he will perhaps be of my mind, when he considers that even motion produces in his mind an idea of succession, no otherwise than as it produces there a continued train of distinguishable ideas. For a man looking upon a body really moving, perceives yet no motion at all, unless that motion produces a constant train of suceossive ideas: v. g, a man becalmed at sca, out of sigiit of land, in a fair day, may look on the sun, or sea, or ship, a whole hour together, and perceive no inotion at all in either; though it be certain that two, and perhaps all of them, have moved during that time a great way. But as soon as he perM 3

ceives either of them to have changed distance with some other body, as soon as this motion produces any new idea in him, then he perceives that there has been motion. “But wherever a man is, with all things at rest about him, without perceiving any motion at all; if during this hour of quiet lie has been thinking, he will perceive the various ideas of his own thoughts in huis own inind, appearing one after another, and thereby observe and find succession where he could observe no motion.

$. 7. And this, I think, is the reason why motions very slow, though they are constant, are not perceived by us; because in their remove from one sensible part, towards another, their change of distance is so slow, that it causes no new ideas in us, but a good while one after another: and so not causing a constant train of new ideas to follow one another immediately in our minds, we have no perception of motion; which consisting in a constant succession, we cannot perceive that succession without a constant succession of varying ideas arising from it.

$. 8. On the contrary, things that move so swift, as not to affect the senses distinctly with several distinguishable distances of their motion, and so cause not any train of ideas in the mind, are not also perceived to move: For any thing that moves round about in a circle, in less time than our ideas are wont to succeed one another in our minds, is not perceived to move; but seems to be a perfect entire circle of that matter or colour, and not a part of a circle in motion. The train of

§. 9. Hence I leave it to others to judge, ideas has a whether it be not probable, that our ideas certain de. do, whilst we are awake, succeed one anogreeofquick. ther in our minds at certain distances, not pess.

much unlike the images in the inside of a lanthorn, turned round by the heat of a candle. This appearance of theirs in train, though perhaps it may be sometimes faster, and sometimes slower, yet, I guess, variçs not very much in a waking man: there seem to be certain bounds to the quickness and slowness of the succession of those ideas one to another in

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our minds, beyond which they can neither delay nor hasten.

9. 10. The reason I have for this odd conjecture, is from observing that in the impressions made upon any of our senses, we can but to a certain degree perceive any succession; which, if exceeding quick, the sense of succession is lost, even in cases where it is evident that there is a real succession. 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 demonstration can be, that it must strike successively the two sides of the room. It is also evident, that it must touch one part of the flesh first, and another after, and so in succession : And yet I believe no-body, who ever felt the pain of such a shot, or heard the blow against the two distant walls, could perceive any succession either in the pain or sound of so swift a stroke. Such a part of duration as this, wherein we perceive no succession, is that which we call an instant, and is that which takes up the time of only one idea in our minds, without the succession of another, wherein therefore we perceive no succession at all.

§. 11.: This also happens, where the motion is so slow, as not to supply a constant train of fresh ideas to the senses, as fast as the mind is capable of receiving new ones into it; and so other ideas of our own thoughts, having room to come into our minds, between those offered to our senses by the moving body, there the sense of motion is lost; and the body, though it really moves, yet not changing perceivable distance with some other bodies, as fast as the ideas of our own minds do naturally follow one another in train, the thing seems to stand still, as is evident in the hands of elocks and shadows of sun-dials, and other constant but slow motions; where, though after certain intervals, we perceive by the change of distance that it hath moved, yet the motion itself we perceive not.

$. 12. So that to me it seems, that the This train constant and regular succession of ideas in a the measure waking inan is, as it were, the measure and of other sucstandard of all other successions : whereof

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if any one either exceeds the pace of our ideas, as where two sounds or pains, &c. take up in their succession the duration of but one idea, or else where any motion or succession is so slow, 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 or, dinary course, come into our mind, between those which are offered to the sight by the different perceptible dis; tances of a body in motion, or between sounds or smells following one another;. there also the sense of a constant continued succession is lost, and we perceive it not but with certain gaps of rest between.

$. 13. If it be so that, the ideas of our The mind

minds, whilst we have any there, do con, long on one stantly change and shift in a continual suca invariable cession, it would be impossible, may any idea.

one say, for a man to think long of any one thing. By, which, if it be mcant, that a man may bave one self-same single idea a long time alone in his mind, without any variation at all, I think, in matter of fact, it is not possible; 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 maķe their appearances) I can give no other reason but experience: And I would have any one try whether he can keep one unvaried single idea in his mind, without any other, 'for any, considerable time together.

§. 14. For trial, let him take any figure, any degree of light or whiteness, or what other he pleases; and he vill, I suppose, find it difficult to keep all other ideas out of his mind : But that some, either of another kind, or various considerations of that idea (each of which considerations is a new idea) will constantly succeed one another in his thoughts, let him be as wary as he can.

§. 15. All that is in a man's power in this case, think, is only to mind and observe what the ideas are that take their turns in l.is understanding; or else to direct the sort, and call in such as he hath a desire or use of: but hinder the constant succession of fresh ones, I think, he cannot, though he may commonly, choose whethier he will heedfully observe and consider them.

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