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pocrates and Sir Isaac Newton. The former of these celebrated authors, in his treatise concerning diet or regimen, observes, that in the nourishment of man, one part repells and another ateracts. And again, in the same treatise, two carpenters, faith he, saw a piece of timber ; one draws, the other pushes; these two actions tend to one and the same end, though in a contrary direction, one up, the other down : This imitates the nature of man: Tv qua có vẻy Axft, cô và cái.
242. It is the general maxim of Hippocrates, that the manner wherein nature acts consisteth in attract. ing what is meet and good, and in repelling what is disagreeable or hurtful.' He makes the whole of the animal economy to be administred by the faculties or powers of nature. Nature alone, faith he, sufficeth for all things to animals. She knows of herself what is necessary for them. Whence it is plain, he means a conscious intelligent nature, that presides and moves the ætherial fpirit. And tho” he declares all things are accomplished on man by necessity, yet it is not a blind fate or chain of mere corporeal causes, but a divine necessity, as he himself expresy calls it. And what is this but an over-ruling intelligent power that disposeth of all things?
243. Attraction cannot produce, and in that sense account for the phænomena, being it self one of the phænomena produced and to be accounted for (n). Attraction is performed by different laws, and cannot therefore in all cases be the effect of the elasticity of one uniform medium. The phænomena of electrical bodies, the laws and variations of magnetism, and, not to mention other kinds, even
(n) 160, 235pa
gravity, is not explained by elasticity, a phænomenon not less obscure than itself. But then, al. though it shews not the agent, yet it sheweth a rule and analogy in nature to say, That the solid parts of animals are endued with attractive powers, where-, by from contiguous Auids they draw like to like; and that glands have peculiar powers attractive of peculiar juices (0). Nacure seems better known and explained by attractions and repulsions, than by those other mechanical principles of size, figure, and the like: that is by Sir Isaac Newton, than Descartes. And natural philosophers excel, as they are more or less acquainted with the laws and methods observed by the author of nature.
244. The size and Mhape of particles and general laws of motion can never explain the secretions without the help of attraction, obscure perhaps as to it's cause, but clear as a law. Numberless instances of this might be given : Lemery, the younger thought himself obliged to suppose, the particles of light or fire (contrary to all reason) to be of a very gross kind, even greater than the pores of the burnt brimstone, in order to account for their being detained or imprisoned therein; but this phænomenon is easily reduced to attraction. There would be no end of enumerating the like cafes, The activity and force of ætherial spirit or fire by the laws of attraction, is imparted to grosser pare ticles (), and thereby wonderfully supports the @oconony of living bodies. By such peculiar compositions and attractions it seems to be effected, that denser fluids can pass where air itself cannot, (18 oil through leather) and therefore through
(p) 152, 163.
atha Galilæi ha and made Newton by "
the nicest and finest strainers of an animal or vege table.
245. The ancients had some general conception of attracting and repelling powers (9) as natural principles. Galilæi had particularly considered the attraction of gravity, and made some discovery of the laws thereof. But Sir Isaac Newton by his fingu. lar penetration, profound knowledge in geometry and mechanics, and great exactness in experiments, hath cart a new light on natural science. The laws of attraction and repulsion were in many instances discovered, and first discovered, by him. He shewed their general extent, and therewith, as with a key, opened several deep secrets of nature, in the knowledge whereof he seems to have made a greater progress, than all the fects of corpuscularians together had done before him. Nevertheless, the principle of attraction itself is not to be explained by physical or corporeal causes.
246. The Cartesians attempted to explain it by the nisus of a subtil element, receding from the center of its motion, and impelling grosser bodies towards it. Sir Isaac Newton in his later thoughts seems (as was before observed to have adopted somewhat not altogether foreign from this notion, ascribing that to his elastic medium (r) which Descartes did to his second element. But the great men of antiquity resolved gravity into the immediate action of an intelligent incorporeal being. To which allo Sir Isaac Newton himself attests and subscribes, although he may perhaps sometimes be thought to forget himself, in his manner of speaking of phyfical agents, which in a strict sense are none at all ; and in supposing real forces to exist in bodies, in
which, to speak truly, attraction and repulsion should be considered only as tendencies or motions, that is, as mere effects, and their laws as laws of motion.
247. Though it be supposed the chief business of a natural philosopher to trace out causes from the effects, yet this is to be understood not of agents (s) but of principles, that is, of component parts, in one sense, or of laws or rules, in another. In strict truth all agents are incorporeal, and as such are not properly of physical consideration. The Aftronomer, therefore, the Mechanic, or the Chemist, not as such, but by accident only, treat of real causes, agents or efficients. Neither doch it feem, as is supposed by the greatest of mechanical philosophers, that the true way of proceeding in their science is, from known motions in nature to investigate the moving forces. Forasmuch as force is neither corporeal, nor belongs to any corporea! thing (1); nor yet to be discovered by experiments or mathematical reasonings, which reach no farther than discernible effects, and motions in things passive and moved.
248. Vis or force is to the soul, what extension is to the body, faith faint Augustin, in his tract concerning the quantity of the Soul, and without force there is nothing done or made, and consequentJy there can be no agent. Authority is not to decide in this case. Let any one consult his own now: tions and reason, as well as experience, concerning the origin of motion, and the respective natures, properties, and differences of foul and body, and he will, if I mistake not, evidently perceive, that there is nothing active in the latter. Nor are they natural
agents or corporeal forces, which make the particles of bodies to cohere. Nor is it the business of experimental philosophers to find them out.
249. The mechanical philosopher, as hath been already observed, inquires properly concerning the rules and modes of operation alone, and not concerning the cause, forasmuch as nothing mechanical is or really can be a cause (u). And although a mechanical or mathematical philosopher may speak, of absolute space, absolute motion, and of force as existing in bodies, causing such motion and proportional thereco ; yet what these forces are, which açe supposed to be lodged in bodies, to be impressed on bodies, to be multiplied, divided, and communicated from one body to another, and which seem to animate bodies like abstract spirits or souls, hath been found very difficult, not to say impossible, foc thinking nien to conceive and explain, as may be seen by consulting Borellus De vi percussionis, and Torricelli in his Lezioni academiche, among other authors.
250. Nor, if we consider the proclivity of mankind to realize their notions, will it seem strange that mechanic philosophers and geometricians should, like other men, be mined by prejudice, and take mathematical hypotheses for real beings existing in bodies, so far as even to make it the very aim and end of their science to compute or measure those phantoms; whereas it is very certain that nothing in truth can be measured * or computed, beside the very effects or motions themselves. Sir Isaac Newton alks, have not the minute particles of bodies certain forces or powers by which they act on
(u) 236, 247. * This subject is handled at large in my Latin tract De motu, pablished above twenty years ago.