HYL. I make no question but they have the same use in all other animals.

PHIL. If so, is it not necessary they should be enabled by them to perceive their own limbs, and those bodies which are capable of harming them?

HYL. Certainly.

PHIL. A mite therefore must be supposed to see his own foot, and things equal or even less than it, as bodies of some considerable dimension; though at the same time they appear to you scarce discernible, or at best as so many visible points?

HYL. I cannot deny it.

PHIL. And to creatures less than the mite they will seem yet larger?

HYL. They will.

PHIL. Insomuch that what you can hardly discern will to another extremely minute animal appear as some huge mountain?

HYL. All this I grant.

PHIL. Can one and the same thing be at the same time in itself of different dimensions?

HYL. That were absurd to imagine.

PHIL. But, from what you have laid down it follows that both the extension by you perceived, and that perceived by the mite itself, as likewise all those perceived by lesser animals, are each of them the true extension of the mite's foot; that is to say, by your own principles you are led into an absurdity.

HYL. There seems to be some difficulty in the point.

PHIL. Again, have you not acknowledged that no real inherent property of any object can be changed without some change in the thing itself?

HYL. I have.

PHIL. But, as we approach to or recede from an object, the visible extension varies, being at one distance ten or a hundred times greater than another. Doth it not therefore follow from hence likewise that it is not really inherent in the object?

HYL. I own I am at a loss what to think.

PHIL. Your judgment will soon be determined, if you will venture to think as freely concerning this quality as you have done concerning the rest. Was it not admitted as a good argument, that neither heat nor cold was in the water, because it seemed warm to one hand and cold to the other?

HYL. It was.

PHIL. Is it not the very same reasoning to conclude, there is no extension or figure in an object, because to one eye it shall seem little, smooth, and round, when at the same time it appears to the other, great, uneven, and regular?

HYL. The very same. But does this latter fact ever happen?

PHIL. You may at any time make the experiment, by looking with one eye bare, and with the other through a microscope.

HYL. I know not how to maintain it; and yet I am loath to give up EXTENSION, I see so many odd consequences following upon such a concession.

PHIL. Odd, say you? After the concessions already made, I hope you will stick at nothing for its oddness. But, on the other hand, should it not seem very odd, if the general reasoning which includes all other sensible qualities did not also include extension? If it be allowed that no idea, nor anything like an idea, can exist in an unperceiving substance, then surely it follows that no figure, or mode of extension, which we can either perceive, or imagine, or have any idea of, can be really inherent in Matter; not to mention the peculiar difficulty there must be in conceiving a material substance, prior to and distinct from extension to be the SUBSTRATUM of extension. Be the sensible quality what it will--figure, or sound, or colour, it seems alike impossible it should subsist in that which doth not perceive it.

HYL. I give up the point for the present, reserving still a right to retract my opinion, in case I shall hereafter discover any false step in my progress to it.

PHIL. That is a right you cannot be denied. Figures and extension being despatched, we proceed next to MOTION. Can a real motion in any external body be at the same time very swift and very slow?

HYL. It cannot.

PHIL. Is not the motion of a body swift in a reciprocal proportion to the time it takes up in describing any given s.p.a.ce? Thus a body that describes a mile in an hour moves three times faster than it would in case it described only a mile in three hours.

HYL. I agree with you.

PHIL. And is not time measured by the succession of ideas in our minds?

HYL. It is.

PHIL. And is it not possible ideas should succeed one another twice as fast in your mind as they do in mine, or in that of some spirit of another kind?

HYL. I own it.

PHIL. Consequently the same body may to another seem to perform its motion over any s.p.a.ce in half the time that it doth to you. And the same reasoning will hold as to any other proportion: that is to say, according to your principles (since the motions perceived are both really in the object) it is possible one and the same body shall be really moved the same way at once, both very swift and very slow. How is this consistent either with common sense, or with what you just now granted?

HYL. I have nothing to say to it.

PHIL. Then as for SOLIDITY; either you do not mean any sensible quality by that word, and so it is beside our inquiry: or if you do, it must be either hardness or resistance. But both the one and the other are plainly relative to our senses: it being evident that what seems hard to one animal may appear soft to another, who hath greater force and firmness of limbs. Nor is it less plain that the resistance I feel is not in the body.

HYL. I own the very SENSATION of resistance, which is all you immediately perceive, is not in the body; but the CAUSE of that sensation is.

PHIL. But the causes of our sensations are not things immediately perceived, and therefore are not sensible. This point I thought had been already determined.

HYL. I own it was; but you will pardon me if I seem a little embarra.s.sed: I know not how to quit my old notions.

PHIL. To help you out, do but consider that if EXTENSION be once acknowledged to have no existence without the mind, the same must necessarily be granted of motion, solidity, and gravity; since they all evidently suppose extension. It is therefore superfluous to inquire particularly concerning each of them. In denying extension, you have denied them all to have any real existence.

HYL. I wonder, Philonous, if what you say be true, why those philosophers who deny the Secondary Qualities any real existence should yet attribute it to the Primary. If there is no difference between them, how can this be accounted for?

PHIL. It is not my business to account for every opinion of the philosophers. But, among other reasons which may be a.s.signed for this, it seems probable that pleasure and pain being rather annexed to the former than the latter may be one. Heat and cold, tastes and smells, have something more vividly pleasing or disagreeable than the ideas of extension, figure, and motion affect us with. And, it being too visibly absurd to hold that pain or pleasure can be in an unperceiving substance, men are more easily weaned from believing the external existence of the Secondary than the Primary Qualities. You will be satisfied there is something in this, if you recollect the difference you made between an intense and more moderate degree of heat; allowing the one a real existence, while you denied it to the other. But, after all, there is no rational ground for that distinction; for, surely an indifferent sensation is as truly a SENSATION as one more pleasing or painful; and consequently should not any more than they be supposed to exist in an unthinking subject.

HYL. It is just come into my head, Philonous, that I have somewhere heard of a distinction between absolute and sensible extension. Now, though it be acknowledged that GREAT and SMALL, consisting merely in the relation which other extended beings have to the parts of our own bodies, do not really inhere in the substances themselves; yet nothing obliges us to hold the same with regard to ABSOLUTE EXTENSION, which is something abstracted from GREAT and SMALL, from this or that particular magnitude or figure. So likewise as to motion; SWIFT and SLOW are altogether relative to the succession of ideas in our own minds. But, it doth not follow, because those modifications of motion exist not without the mind, that therefore absolute motion abstracted from them doth not.

PHIL. Pray what is it that distinguishes one motion, or one part of extension, from another? Is it not something sensible, as some degree of swiftness or slowness, some certain magnitude or figure peculiar to each?

HYL. I think so.

PHIL. These qualities, therefore, stripped of all sensible properties, are without all specific and numerical differences, as the schools call them.

HYL. They are.

PHIL. That is to say, they are extension in general, and motion in general.

HYL. Let it be so.

PHIL. But it is a universally received maxim that EVERYTHING WHICH EXISTS IS PARTICULAR. How then can motion in general, or extension in general, exist in any corporeal substance?