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 space?  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 space 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.