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 embarrassed: 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 assigned 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.