World of Air exteriously; for Natures motions are not all external or perceptible by our senses, neither are they all circular, or onely of one sort, but there is an infinite change and variety of motions; for though I say in my Philosophical opinions,[4] _As there is but one onely Matter, so there is but one onely Motion_; yet I do not mean, there is but one particular sort of motions, as either circular, or straight, or the like, but that the nature of motion is one and the same, simple and intire in it self, that is, it is meer motion, or nothing else but corporeal motion; and that as there are infinite divisions or parts of matter, so there are infinite changes and varieties of motions, which is the reason that I call motion as well infinite as matter; first that matter and motion are but one thing, and if matter be infinite, motion must be so too; and secondly, that motion is infinite in its changes and variations, as matter is in its parts. And thus much of motion for this time; I add no more, but rest, Madam, _Your faithful Friend,_ _and Servant._ [1] _Philos. p._ 2. _Art._ 25. [2] _Art._ 40. [3] _Philos. part._ 2. _a._ 54. [4] _Part._ 1. _c._ 5. XXXI. _MADAM,_ I observe your _Author_ in his discourse of Place makes a difference[1] betwixt an _Interior and Exterior place_, and that according to this distinction, _one body may be said to change, and not to change its place at the same time, and that one body may succeed into anothers place_. But I am not of this opinion, for I believe not that there is any more place then body; as for example, Water being mix'd with Earth, the water doth not take the Earths place, but as their parts intermix, so do their places, and as their parts change, so do their places, so that there is no more place, then there is water and earth; the same may be said of Air and Water, or Air and Earth, or did they all mix together; for as their bodies join, so do their places, and as they are separated from each other, so are their places. Say a man travels a hundred miles, and so a hundred thousand paces; but yet this man has not been in a hundred thousand places, for he never had any other place but his own, he hath joined and separated himselfe from a hundred thousand, nay millions of parts, but he has left no places behind him. You will say, if he travel the same way back again, then he is said to travel thorow the same places. I answer, It may be the vulgar way of expression, or the common phrase; but to speak properly, after a Philosophical way, and according to the truth in nature, he cannot be said to go back again thorow the same places he went, because he left none behind him, or els all his way would be nothing but place after place, all the hundred miles along; besides if place should be taken so, as to express the joyning to the neerest bodies which compass him about, certainly he would never find his places again; for the