gular 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 times; 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 twenty-four hours had been irrecoverably lost to them, and been for ever left out of their account of time.

The idea of

succession

not from

motion.

§ 6. Thus, by reflecting on the appearing of various ideas one after another in our understandings, we get the notion of succession; which, if any one would think 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 successive ideas: v. g. a man becalmed at sea, out of sight of land, in a fair day, may look on the sun, or sea, or ship, a whole hour together, and perceive no motion 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 perceives 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 he has been thinking, he will perceive the various ideas of his own thoughts in his own mind, 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

VOL. I.

N

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 ideas has a certain degree of quickness.

§ 9. Hence I leave it to others to judge whether it be not probable that our ideas do, whilst we are awake, succeed one another in our minds at certain distances, not much unlike the images in the inside of a lantern 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, varies 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 our minds, beyond which they can neither delay nor hasten.

§ 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 nobody 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 may 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 clocks 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 constant and regular succession of ideas in a waking man is, as it were, the measure and standard of all other successions: whereof 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 ordinary course, come into our

This train

the measure

of other successions.

mind between those which are offered to the sight by the different perceptible distances 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.

The mind cannot fix

long on one invariable

idea.

§ 13. If it be so that the ideas of our minds, whilst we have any there, do constantly change and shift in a continual succession, it would be impossible, may any one say, for a man to think long of any one thing. By which, if it be meant that a man may have 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 make their appearances) I can give no other reason but experience: and 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 will, 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, I think, is only to mind and observe what the ideas are that take their turns in his 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 whether he will heedfully observe and consider them. Ideas, however made,

§ 16. Whether these several ideas in a man's mind be made by certain motions,

include no

sense of mo

tion.

I will not here dispute: but this I am sure, that they include no idea of motion in their appearance; and if a man had not the idea of motion otherwise, I think he would have none at all; which is enough to my present purpose, and sufficiently shows 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 succession and duration, without which we should have no such ideas at all. It is not then motion, but the constant train of ideas in our minds, whilst we are waking, that furnishes us with the idea of duration; whereof motion no otherwise gives us any perception than as it causes in our minds a constant succession of ideas, as I have before showed: and we have as clear an idea of succession and duration, by the train of other ideas succeeding one another in our minds, without the idea of any motion, as by the train of ideas caused by the uninterrupted sensible 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.

Time is duration set out by mea

sures.

§ 17. Having thus got the idea of duration, the next thing natural for the mind to do is to get some measure of this common duration, whereby it might judge of its different lengths, and consider the distinct order wherein several things exist, without which a great part of our knowledge would be confused, and a great part of history be rendered very useless. This consideration of duration, as set out by certain periods, and marked by certain measures or epochs, is that, I think, which most properly we call time.

§ 18. In the measuring of extension there is nothing more required but the application of the standard or measure we make use of to the thing of whose extension we would be informed. But in the measuring of duration this cannot be done,

A good measure of time must divide its whole duration into equal periods,