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in horfes and pigeons, that bitter humour is not ufually, as in man, col- PHYSICS. lected into one bag: and tho' it be fo in vipers; yet, as far as I have obferv'd, the containing cyftis does not at all touch the liver.

3dly, "Tis difficult to determine the true and primary use of a part; because nature often fits one part for several uses.

And, 4thly, it fometimes increases the difficulty, that nature may compafs the fame ends by feveral means; each of them fufficiently commodious. I join these two obfervations together, becaufe, in effect, they often concur to render it hard to determine the true ufe of a part. Neither does nature conftantly employ only one part to perform a particular office; but the defign'd effect is, fometimes, produced by a series of fucceffive operations, to which feveral parts may differently contribute.

Neither the mechanifm of a human body, nor of very confiderable parts thereof, is to be affign'd from the bare ftructure of the vifible matter, whether folid, or fluid, to be found in the veffels, and cavities of a dead body, skilfully diffected. For the body of a living man is a very compounded engine, many of whose functions are perform'd, not by the blood, and other vifible fluids, barely as they are liquors; but, partly, by their circulation, and other motions; and, partly, by a very agile, and invisible, fort of fluids, call'd fpirits animal and vital; partly, perhaps, by little fpringy particles; by fomewhat that may be call'd the vital portion of the air; and, by things analogous to local ferments: the important operations of all which, ceafe with life; and the agents themselves are not to be difcern'd in a dead carcafs. So that, befides those manifeft ufes, which the visible fabric of the engine may fuggeft to an anatomift; there may be chymical ufes of fome parts, that ferve for the elaboration of fpirits, and other fluids: which ufes, as we formerly obferv'd, are not fuggefted to the anatomift, by the infpection of the ftructure of the parts; but, to difcern them, may require no ordinary skill in chymical principles, and operations.

Such confiderations as thefe, lead me to think it exceeding difficult to determine, with any certainty, the principal ufe of many particular parts; efpecially, if other ufes be excluded. It is not enough to fecure us, that we understand the chief function, and end, of a part, to know, that it is contrived for fuch a purpofe; fince this fitnefs hinders not, but that the primary use of the part may be another more conducive to the general welfare of the animal, or the cofmical ends of nature. And it ought not to feem ftrange, that fome pieces of workmanship, confifting of many parts, all of them curioufly contrived, fhould, by one learned man, be guefs'd to be defign'd for this ufe; and, by others, for that; while both of them may be worthy of the artificer.

When fome very politic prince does a great thing, without declaring why; the gueffes of the statesmen are often very different; tho' none of them afcribe to him a defign unbecoming a wife man. So, when a learned author expreffes himself ambiguoufly; one reader interprets his words to this fenfe; and another, to that: yet both of the fenfes pitch'd on, VOL. II.

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may

PHYSICS. may fairly agree with the context, and the main fcope of the writer. This I fay, because I would, by no means, difparage the wifdom of nature, by propofing the difficulties I have hitherto mentioned; tho', I confefs, that, upon the account of them, and fome others; I look upon many of the arguments that feveral authors draw from final caufes, but as conjectures. And, in many cafes, I allow what is fuggefted to me, upon the fuppofition of the intended ufes of particular parts, rather as proper hints to excite, and direct, a more thorough inquiry, than as fafe grounds to build phyfical conclufions on.

PROP. V..

The naturalift should not fuffer the fearch, or difcovery, of final caufes, to make him undervalue, or neglect, the inquiry after their efficients.

Tis true, to inquire for what purpofe nature would have particular effects produced, is a curiofity worthy of a rational creature. But this is not the proper task of a naturalift; whofe work is not fo much to difcover the manner wherein, as for what reafon particular effects are produced. Thus, an ignorant ruftic, in England, knows fomething of a watch, if he is able to tell you, that 'tis an inftrument made to measure time; which is more than every American favage would be able to fay; and more than those civiliz'd Chinese knew, who took the firft watch they faw for a living creature: yet the English ruftic, who knows no more of a watch, than that 'twas made to fhew the hour of the day, understands but very little of the nature of that machine. And, as the two things men aim at in physics, are to understand after what manner nature produces the phenomenon we contemplate; and, in cafe it be imitable by us, how we may, if occafion requires, produce the like effect, or come near it; thefe ends cannot be attain'd by the bare knowledge of the final caufes of things, nor of the general efficient. But, to answer those intentions, we must know the particular, efficients, with the manner, and progrefs, of their operating; and what difpofitions they either find, or produce in the matter they work on. Thus, he who would thoroughly understand the nature of a watch, must not reft fatisfy'd with knowing, in general, that a man made it for fuch ufes; but he muft, particularly, know of what materials the fpring, the wheels, the chain, and the balance are made; he must know the number of the wheels, their magnitude, fhape, fituation, and connexion, in the engine; and after what manner one part moves another, in the whole feries of motions; from the expanfive endeavour of the fpring, to the revolutions of the index that points the hours. And much more must a mechanic know all this, if he means to make a watch himself, or to give fufficient inftructions for it to be made. In fhort, the neglect of efficient caufes, would render philofophy ufelefs; but the ftudious fearch after them, will not prejudice the contemplation of final caufes. For the wife author of nature has fo excellently contriv'd the univerfe, that the more clearly, and particularly, we difcern how fuitable the means are to the

ends.

ends to be obtain'd by them; the more plainly we difcern the admirable PHYSICS. wisdom of the author of things; who is "wonderful in counfel, and excellent in working." Nor will the fufficiency of the intermediate caufes make it needless to admit a firit, and fupreme caufe; fince that order of things, by virtue whereof thefe means become fufficient to fuch ends, muft have been, at firft, inftituted by an intelligent caufe. And if it be irrational to afcribe the excellent fabric of the univerfe, and the actions that have manifeft tendencies to determinate useful ends, to fo blind a cause as chance; it will be rather more irrational to afcribe to chance, the firft formation of the univerfe; of which the prefent ftate of things is but the natural confequence, or effect. For it may, indeed, be plaufibly faid, that, in the prefent ftate of things, the feveral parts of the univerie are, by the contrivance of the whole, determin'd, and thereby qualify'd to obtain their ends; but it cannot be, rationally, pretended, that, at the firft formation of the world, there was a fufficiency in the fenfelefs materials of it, without any particular guidance of a wife fuperintendent, to frame bodies which are fo excellently contriv'd, and fitted to their refpective ends.

Upon the whole, it appears, that all confideration of final caufes, is not to be banish'd from natural philofophy; but that 'tis rather allowable*, and, in fome cafes, commendable, to argue, from the manifeft ufes of things, that the author of nature pre-ordain'd them; that the fun, and moon, with the other celeftial bodies, excellently declare the power, wifdom, and glory of God; and were, fome of them, among other purpo fes, made to be ferviceable to man; that, from the fuppos'd ends of inanimate bodies, whether celeftial, or fublunary, 'tis very unfafe to draw arguments, to prove the particular nature of those bodies, or the true system of the univerfe; that, as to animals, and the more perfect fort of vegetables, 'tis warrantable to fay, particular parts were preordained to particular ufes, relating to the welfare of the animal, or

*Final caufes are allowable in philofophy; and Sir Ifaac Newton himself, fcruples not to affign them in the ftructure and contrivance of the universe. And of this we have a remarkable example in his doctrine of comets. "Comets, (fays "that admirable philofopher) by reafon "of the great number of them, the vast "diftance of their aphelia from the fun,

and the confiderable stay they make "there, muft neceffarily receive fome di"fturbance from their mutual gravita"tions to each other. Whence their ec"centricities, and times of revolution, "will fometimes be a little increas'd, and

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"at others, diminish'd. We are not,
"therefore, to expect, that the fame co-
"met fhall always exactly return in
"the fame orbit, at the fame period
"of time.- And hence appears the
"reason why comets move not in the
"zodiac, as the planets do; but ftray
"from it, in various motions, to all the

parts of the heavens: for, in their a

phelia, where their motion is flowest, "they ought to be at the greateft di"ftance from one another, that their "mutual attractions may be the lefs. Newton. Princip. p. 480.

plant

PHYSICS. plant itfelf, or to its fpecies; but that fuch arguments may eafily deceive, if those who form them are not very cautious to avoid miftaking, among the various ends that nature may have in the contrivance of an animal body, and the various ways which fhe may fuccefsfully take to compafs the fame ends; and laftly, it appears, that a philofopher, neverthelefs, muft not let the fearch, or knowledge of final caufes, make him neglect a careful inquiry after efficients.

THINGS

THINGS

ABOVE

REASON,

CONSIDER'D.

SECT. I.

kinds.

T appears to me, that, among the objects of our reafon, there are Things above fome, whofe nature we cannot comprehend; others, whofe attri- reason, of three butes, or actions, we cannot reconcile to the fubject; and, lastly, others, that we cannot conceive how they should confift with fome acknowledg'd truth: and thefe may be call'd things above reafon. By which I here underftand, not fuch things as are falfe, and abfurd; but fuch as, tho' the understanding fees fufficient caufe to affent to, yet finds itself reduced to this affent, with a remarkable, and peculiar, difadvantage. And this difadvantage, ufually, proceeds either from the nature of the thing propofed; which is fuch, that we cannot, fufficiently, comprehend it; or, from our being unable to conceive the manner of its exiftence, and operation; or, becaufe it involves fome notion, or propofition, that we fee not how to reconcile with fome other, which, we are perfuaded, is true. The first of these three forts of things, may be call'd incomprehenfible; the fecond, inexplicable; and the third, unfociable.

The first confifts of those things, whofe nature is not distinctly, and ad- Incomprehenfible. equately, comprehenfible by us; to which, perhaps, we may refer all fuch intellectual Beings, if any be granted, as are, by nature, of an higher order than human fouls; at leaft, we may refer to this head the great author of nature.

The second fort of things above reafon, confifts of fuch as, tho' we do not Inexplicable. deny to exift, yet we cannot clearly, and fatisfactorily, conceive how they can be what we acknowledge they are: as, how matter can be infinitely divisible; and how there fhould be fuch an incommenfurability betwixt the fide, and diagonal, of a fquare, that the fmalleft line cannot, adequately, measure them both.

The

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