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pocrates and fir Isaac Newton. The former of. these celebrated authors, in his treatise concerning diet or regimen, observes, that in the nourilhment of man, one part repells and another attracts. And again, in the same treatise, two carpenters, faith he, faw 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,: an qua Hày 2Axol, đề 8 :. . . 242. It is the general maxim of Hippocrates, that the manner wherein nature acts consisteth in attracting 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 faculcies or powers of nature. Nature alone, faith he, fufficeth 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 neceffity, yet it is not a blind fate or chain of mere corporeal causes, but a divine neceflity, as he himself expresy calls it. And what is this but an over-ruling intelligent power that dirposeth of all things ?

243. Attraction cannot produce, and in that sense account for the phænomena, being ic 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, 235.2

gragravity, is not explained by elasticity, a phæno menon not less obscure than itself. But then, although it shews not the agent, yet it Theweth a rule and analogy in nature to say, That the solid parts of animals are endued with attractive powers, where*by from contiguous fluids they draw like to like; and that glands have peculiar powers attractive of peculiar juices (). Nature feems better known and explained by attractions and repulsions, than by those other mechanical principles of size, figure, and the like: that is by fir 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 shape 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 inftances of this might be given : Lemery the young. er 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 phæ. nomenon is easily reduced to attraction. There would be no end of enumerating the like cases. * The activity and force of ætherial spirit or fire by the laws of attraction, is imparted to grosser par. ticles (D), and thereby wonderfully supports the @conony of living bodies. By such peculiar compositions and attractions it seems to be effected, that denser Aluids can pafs where air itself cannot, (as oil through leather) and therefore through

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the nicest and finest strainers of an animal or vegetable.

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 fir Isaac Newton by his singular penetration, profound knowledge in geometry and mechanics, and great exactness in experiments, hath cast a new light on natural science. The laws of attraction and repulfion were in many instances discovered, and first discovered, by him. He Thewed 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 sects 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 Del cartes did to his second element. But the great men of antiquity resolved gravity into the immediate action of an intelligent incorporeal being. To which also 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

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which, to speak truly, attraction and repullon fhould be considered only as tendencies or motions, that is, as mere effects, and their laws as laws of motion.

247. Though it be fuppofed 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 fense, or of laws or rules, in another. In strict truth all agents are incorporeal, and as such are nor properly of physical consideration, The Astronomer, therefore, the Mechanic, or the Chemit, not as such, but by accident only, treat of real causes, agents or efficients. Neither doth 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 corporeal thing (t); nor yet to be discovered by experiments or mathematical reasonings, which reach no farther than discernable effects, and motions in things paffive and moved. • 248. Vis or force is to the soul, what extenfion 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 consequently there can be no agent. Authority is not to de cide in this case, Let any one consule his own notions and reason, as well as experience, concerning the origin of motion, and the respective natures, properties, and differences of foul and body, and be will, if I mistake not, evidently perceive, that there is nothing active in the latter. Nor are they natural

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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 cons cerning 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 thereto; yet what these forces are, which are 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, for thinking men 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 misled 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 asks, 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, published above twenty years ago.

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