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BOOK nearer to the centre; which is all that Des Cartes means
- by gravity. But of this afterwards. N.40. The last fundamental law of motion is, That when a
body meets another, if it hath not a greater power to proceed in a right line than the other hath to hinder it, then it turns aside, but loseth not its motion ; if it hath a greater force than the other, then it communicates its motion to the other, and loseth itself as much as it gives. The reason given of this is, because it is the immutable will of God, that the same quantity of motion shall be always preserved : of which I have spoken already.
And as to the whole matter of these laws of motion, Mr. Boyle Mr. Boyle saith, That they have been received by of Venera. tion, &c. learned men, rather upon the authority of so famous
a mathematician, than upon any convictive evidence which accompanies the rules themselves.
The next thing we are to do is, to see whether, from these laws of motion, he gives a satisfactory account of the making of the universe.
And here we must consider the elements out of which he supposeth it made, and the account of the things . made out of them.
As to the elements, this, in short, is his account of Cart. Prin- them. The particles of matter into which it was first ül. n.48. divided, could not at first be round, because then there
must be a vacuum between them ; but they must by succession of time become round, because they had various circular motions, (although the natural motion be in a right line, and God's immutable will be that
every thing should be preserved in its natural state.) N. 49. But that force which put them into these motions was
great enough to wear off their angles, and so they become round: which being joined together, must leave some intervals, which were filled up by the filings off from the angles ; which were very small, and of a
figure fit to fill up all interstices, and were carried chAP. about with a very quick motion. . So that here we have __ two elements; one of the round particles, and another of the subtle ethereal matter, which came by the attrition of the first particles. But besides these, there are N. 52. others more gross and unapt for motion by their figure, and which make the third element; and out of these all the bodies of the visible world are composed; the sun and fixed stars out of the first; the heavens out of the second ; and the earth, with comets and planets, out of the last.
The main thing which makes this hypothesis unsatisfactory to me is, that it is as precarious and groundless as the Epicurean, and they differ only as to the beginning of motion; which the Epicureans suppose to belong to matter : and Des Cartes saith, it comes from an infinite agent distinct from it; because he supposes that it would not move of itself, unless it were put into motion. Which being set aside, there is no more of the wisdom or providence of God to be found in his making of the world than the others, nor any more evidence as to the production of his elements : for he first.supposes
only from his mathematical notion of body consisting only in extension, and from hence he undertakes to give an account, not of God's creating the matter of the world at once, nor of his production of things within six days, but how, in process of time, particles of matter being divided, would come to make up his several elements. And for this he makes use of several suppositions, without any ground of reason why it must be so, and no otherwise; which was the thing which he undertook to Mersennus to do. For what reason doth he give that matter must be divided at first, in order to the production of the elements ? When there
BOOK can be no division, but there must be intervals between
the parts; and if all matter be one and the same, and the space of the intervals be necessarily filled up with extended matter, what division of parts could there be?
And how can that extension be divided into solid bodies ? Part. iii. Des Cartes grants, That by reason we cannot find out
how big the parts of matter were at first, how quick their motion, nor what kind of circles they described, then it is impossible to find out by reason how the world was made. For if God, as he confesses, might use innumerable ways of doing it, and we cannot tell which he pitched upon, what a vain thing is it in any
man to undertake to give an account how the world Tract. Phy- came to be formed ? And therefore Rohault, with great sic. c. 21.
judgment, pretends not to give an account how matter was formed by God at the first creation, but only to shew a possibility how it might be framed, so as to solve the appearances of the world. But neither he nor Des Cartes can reconcile this primitive division of matter into parts with their original notion of matter; which is nothing but extension. But if matter be so divided, as Des Cartes supposes, may we not reasonably conclude that there were three such elements as he speaks of? The question is not, whether there be not a distinction of the particles of matter answerable to these three elements, viz. a more subtle and ethereal substance, as in fire; a less subtle and globular, as in air; a grosser, as in earth; which are most made according to these principles out of such different particles : but the point is, whether these elements can be produced in such a manner by the mere motion of matter? And Des Cartes will by no means allow them to be made round, for fear of his vacuum, which would spoil all, but that by
length of time they would become round; nay, they N. 48. must become round; Eas non potuisse successu tem
poris non fieri rotundas, are his words. Now here lies CHAP. the difficulty, to shew how these must become round by his own laws of motion, i. e. by a motion in a right line; for he saith, It is done by various circular motions. But how comes the original matter of itself to deviate from the fundamental law of motion ? That is, from whence came these circular motions, without which the elements could not be formed ? And if the first particles were so solid as is supposed, how came the angles to be worn off? For, when two solid bodies meet, according to his own laws of motion, the one communicates motion to the other, and loses of its own; which implies nothing but a mutual contact and rebounding upon the collision; but this doth by no means shew how these bodies come to wear off each other's angles : and therefore this is only a product of fancy, but very necessary to his purpose. But let us suppose, that by frequent collisions some alterations would be made in the figure of these bodies, what a long time must it be before they become spherical! Too long to be consistent with such a thing as creation; which at the same time is pretended to be believed. But the only agreeable supposition to this is, the existence of matter from eternity, which having, we know not how many ages since, been put into motion then by a casual concourse, (for it was not by the laws of motion,) these particles justling one against another, at last rubbed off the uneven particles, so as to make them round. But what quantity was there of such particles, in proportion to what was left ? For it may easily be too great, and so the first element Enchirid.
Metaphys. be too powerful for the second, as some have under-c. 16. taken to demonstrate that it must be, upon Des Cartes's 2
Philosoph. own grounds. And the answer given is insufficient ; Cartes. c. 6. because the proportion of the first element will still be too great, notwithstanding all the uses found out for it;
BOOK and therefore Rohault more wisely avoided these at
-tempts of forming the world out of the first chaos of egis Ro confused matter, which he found could give no satisfacponse, ch. Com 6. art. 2. tion.
Let us now, in the last place, come to the account he gives of the phænomena of the universe, according to these principles. And because it would be too large a task to run through all, I shall confine myself to these following: 1. The formation of the sun and stars. 2. The motion of the air. 3. The placing of the earth. 4. The mechanism of animals.
As to the formation of the sun and stars; which
i. Des Cartes saith was in this manner: That the matter cip. par. iii. De D. 54 of the first element increased by the attrition of the
particles of the second ; and there being greater quantity of it than was necessary to fill up the interstices between the round particles of the second element, the
remainder went to the centres of the several vortices. N. 88. But here arises a difficulty, which takes away any ap
pearance of satisfaction in this matter; which is, that Des Cartes owns, that in this matter of the first element there are some parcels which are less divided and slower moved, having many angles, and therefore unfit for motion. Now why should not these take up the centre of the vortex, and not those which have a quicker motion, and endeavour to recede from it? For we must observe, that Des Cartes supposes that these bigger fragments are mixed with the lesser, and that they transfer their motion to them: according to the laws of nature (which serve his turn as he pleases) greater bodies do easier transfer their motion to lesser, than receive motion from them. So that here we have these bigger fragments of the first element mixed with the lesser, and communicating their motion to them. Now who could expect any other than that these should have