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pocrates and Sir Ifaac Newton. The former of thefe celebrated authors, in his treatise concerning diet or regimen, obferves, that in the nourishment of man, one part repells and another attracts. And again, in the fame treatife, two carpenters, faith he, faw a piece of timber; one draws, the other pushes; thefe two actions tend to one and the fame end, though in a contrary direction, one up, the other down: This imitates the nature of man: πνεῦμα τὸ μὲν ἕλκει, τὸ δὲ ὠθέει.

242. It is the general maxim of Hippocrates, that the manner wherein nature acts confifteth in attract ing what is meet and good, and in repelling what is difagreeable or hurtful. He makes the whole of the animal economy to be adminiftred by the faculties or powers of nature. Nature alone, faith he, fufficeth for all things to animals. She knows of herself what is neceffary for them. Whence it is plain, he means a confcious intelligent nature, that prefides and moves the etherial 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 caufes, but a divine neceffity, as he himself exprefly calls it. And what is this but an over-ruling intelligent power that dif pofeth of all things?

243. Attraction cannot produce, and in that sense account for the phænomena, being it felf one of the phænomena produced and to be accounted for (n). Attraction is performed by different laws, and cannot therefore in all cafes be the effect of the elafticity of one uniform medium. The phænomena of electrical bodies, the laws and variations of magnetifm, and, not to mention other kinds, even

(n) 160, 235.

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gravity, is not explained by elafticity, a phænomenon not lefs obfcure than itself. But then, although it fhews not the agent, yet it fheweth a rule and analogy in nature to fay, That the folid parts of animals are endued with attractive powers, whereby from contiguous fluids they draw like to like; and that glands have peculiar powers attractive of peculiar juices (o). Nature feems better known and explained by attractions and repulfions, than by those other mechanical principles of fize, figure, and the like that is by Sir Ifaac Newton, than Defcartes. And natural philofophers excel, as they are more or lefs acquainted with the laws and methods obferved by the author of nature.

244. The fize and fhape of particles and general laws of motion can never explain the fecretions without the help of attraction, obfcure perhaps as to it's caufe, but clear as a law. Numberless inftances of this might be given: Lemery the younger thought himself obliged to fuppofe, the particles of light or fire (contrary to all reason) to be of a very grofs kind, even greater than the pores of the burnt brimstone, in order to account for their being detained or imprisoned therein; but this phanomenon is easily reduced to attraction. There would be no end of enumerating the like cafes, The activity and force of ætherial fpirit or fire by the laws of attraction, is imparted to groffer particles (p), and thereby wonderfully fupports the coconony of living bodies. By fuch peculiar compofitions and attractions it feems to be effected, that denfer fluids can pafs where air itself cannot, (as oil through leather) and therefore through.

(0) 41.

(p) 152, 163.

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the niceft and fineft ftrainers of an animal or vegetable.

245. The ancients had fome general conception of attracting and repelling powers (9) as natural principles. Galilæi had particularly confidered the attraction of gravity, and made fome discovery of the laws thereof. But Sir Ifaac Newton by his fingular penetration, profound knowledge in geometry and mechanics, and great exactnefs in experiments, hath caft a new light on natural fcience. The laws of attraction and repulfion were in many inftances difcovered, and first discovered, by him. He fhewed their general extent, and therewith, as with a key, opened feveral deep fecrets of nature, in the knowledge whereof he seems to have made a greater progrefs, than all the fects of corpufcularians together had done before him. Nevertheless, the principle of attraction itself is not to be explained by phyfical or corporeal caufes.

246. The Cartefians attempted to explain it by the nifus of a fubtil element, receding from the center of its motion, and impelling groffer bodies towards it. Sir Ifaac Newton in his later thoughts feems (as was before obferved) to have adopted fomewhat not altogether foreign from this notion, afcribing that to his elaftic medium (r) which Def cartes did to his fecond element. But the great men of antiquity refolved gravity into the immediate action of an intelligent incorporeal being. To which alfo Sir Ifaac Newton himself attefts and fubfcribes, although he may perhaps fometimes be thought to forget himself, in his manner of fpeaking of phyfical agents, which in a strict sense are none at all; and in fuppofing real forces to exist in bodies, in

(?) 241, 242. (r) 237, 238.

which, to speak truly, attraction and repulfion fhould be confidered 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 philofopher 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 fenfe, or of laws or rules, in another. In ftrict truth all agents are incorporeal, and as fuch are not properly of phyfical confideration. The Aftronomer, therefore, the Mechanic, or the Chemift, not as fuch, but by accident only, treat of real caufes, agents or efficients. Neither doth it feem, as is fuppofed by the greatest of mechanical philofophers, that the true way of proceeding in their fcience is, from known motions in nature to inveftigate the moving forces. Forafmuch as force is neither corporeal, nor belongs to any corporeal thing (f); nor yet to be discovered by experiments or mathematical reafonings, which reach no farther than difcernible effects, and motions in things paffive and moved.

248. Vis or force is to the foul, 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 confequently there can be no agent. Authority is not to decide in this cafe. Let any one confult his own notions and reason, as well as experience, concerning the origin of motion, and the refpective 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 (t) 220.

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agents or corporeal forces, which make the particles of bodies to cohere. Nor is it the business of experimental philofophers to find them out.

249. The mechanical philofopher, as hath been already obferved, inquires properly concerning the rules and modes of operation alone, and not concerning the caufe, forafmuch as nothing mechanical is or really can be a cause (u). And although a mechanical or mathematical philofopher may speak of abfolute space, abfolute motion, and of force as exifting in bodies, caufing fuch motion and proportional thereto; yet what thefe forces are, which are fuppofed to be lodged in bodies, to be impreffed on bodies, to be multiplied, divided, and communicated from one body to another, and which feem to animate bodies like abftract fpirits or fouls, hath been found very difficult, not to fay impoffible, for thinking men to conceive and explain, as may be feen by confulting Borellus De vi percuffionis, and Torricelli in his Lezioni academiche, among other authors.

250. Nor, if we confider the proclivity of mankind to realize their notions, will it feem ftrange that mechanic philofophers and geometricians fhould, like other men, be milled by prejudice, and take mathematical hypothefes for real beings exifting in bodies, fo 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, befide the very effects or motions themselves. Sir Ifaac Newton afks, have not the minute particles of bodies certain forces or powers by which they act on

(u) 236, 247.

This fubject is handled at large in my Latin tract De motu, published above twenty years ago.

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