That we be not Over hasty in Concluding, nor too Positive in Asserting, that This or That must be, or is, the particular Destinated Vse of such a Thing, or the Motive that induc’d the Author of Nature to Frame it thus.
IT has been above declar’d, That some Parts are so Excellently, and so Manifestly, Fitted for a certain Use, as the Eye for Seeing; and so much better Fitted for That, than for any Other; that ‘twere little less than Heedlesness or Perverseness, to Doubt of Its being Destinated Thereto. But the like cannot be said of all the Other Parts of the Body, especially of the Internal. And there are divers Uses, either Necessary, or highly Conducive, to the Welfare of the Animal, to which no One Part is so much more conspicuously Fitted than any Other, but that ‘tis more Difficult than many think, to determine the True and Primary Uses or Offices of some Parts, especially with so much Certainty, as thereon to ground Physiological Inferences: And of this Difficulty I conceive there may be four Reasons, tho’ they do not All, nor perhaps Most of them, occurr in Each particular Case.
And First, the whole Animal it self, the Use of whose particular Parts is under inquiry, is but a Part of that greater Body, the Vniverse; and therefore cannot easily be suppos’d, to have been fram’d and furnish’d with the Parts it consists of, meerly for its own sake. And when we say, that all its Parts are Contriv’d for the best Advantage for the Animal, I conceive it is to be understood in this Limited Sense; That the Parts are excellently fram’d for the Welfare of the Animal, as far forth as That Welfare is consistent with the General Ends of the Author of Nature, in the Constitution and Government of the Universe: which Ends, because they relate to the whole World, or to very considerable Masses of it, as the Terraqueous Globe, the Planets, and other Stars, I have formerly, for brevity’s sake, styl’d Cosmical: And tho’ it has not been prov’d, that None of these Cosmical Ends are investigable by us: yet to discover them All, is not an easie Task. And yet it seems presumptuous to suppose, that the Welfare of particular Animals is any further design’d and provided for, than will consist with the Cosmical Ends of the Universe, and the Course of Gods General Providence; to which his Special or Particular Providence, about this or that meer Animal, ought in reason to be Subordinated. And tho’ I think it a great Rashness for us men to Determine positively, and exclusively to others, what Ends the Omniscient Creator propos’d to himself, in giving to the World the Frame we see it has; yet, as far as I can hitherto discern, I see nothing that is more likely to have been One Grand Motive of so great a Variety as we may observe in his Corporeal Works, especially in Animals, than that which hath in part been elsewhere intimated, viz. That He might, by so many and so very differing Contrivances, as are to be met with in the Structure of Men, Four-footed Beasts, Birds, Fishes, Reptiles, &c. Exercise and Display (what could not be by a less Variety so fully manifested) that which an Apostle, (Ephes. 3.10) speaking of things of another Order, Emphatically styles the […] (the Multifarious or Manifold Wisdom of God.) Man being acknowledg’d, upon the account of his very Body, the most Perfect of Animals; if God had simply Design’d the giving of every Animal, the most Advantageous Structure that could be devis’d, it seems that He should have Made no Other Animals than Men. But then there could not have been that Diversity of Contrivance among Living Automata, that does so much recommend the Wisdom of Him, that could Frame so Many and so Differing Animals, tho’ not All of them equally Perfect, yet All of them admirably Furnish’d for those Purposes to which He Destinated them. And therefore it does not argue any Want of Providence, that He has not Furnish’d Man with Wings, as he hath Birds; nor Fishes with four Feet; nor Birds with Fins and Scales: because these Parts would have been either Superfluous and Burthensom, or would not have Suited with his Design, of making Some Animals Live on the Earth, and Some in the Water: And if He Design’d any to Live, tho’ not equally, in Both, He furnish’d Them with Parts of a Peculiar Structure, as I have elsewhere noted of the Beaver and the Frog. If it were not for the forementioned Consideration, ‘twould be hard to give a Reason, why Vegetables were not made the Food of all Animals; But Some should be Carnivorous, and furnish’d with Appetites and Organs to Devour Others, and Live, as Birds and Beasts of Prey do, upon the Destruction of the Weaker. And ‘twill be hard to shew, why, even in Animals of the same Kind, the Safety of Some should be so much better Provided for than that of Others; as We see, that some Ants, and some Glow-worms, are Furnish’d with Wings; and Some not. And in Mankind itself, Those of the Female Sex are not so happily Fram’d, in order to their own Welfare, as Those of the Masculine: Since the Womb, and other Things peculiar to Women, which are not Necessary to the Good of Individual Persons, but to the Propagation of their Species, subject that tender Sex to a whole Set of Diseases, belonging to them either peculiarly, as they are Women, or as they are with Child, or brought to Bed; from all which Men are exempt. So that, to apply these Things to Our present Purpose; Men may sometimes Mistake, when they peremptorily Conclude, that This or That Part of an Animal Must, or Cannot, have been Fram’d for such an Use, without Considering the Cosmical, and therefore Primary and Over-ruling, Ends, that may have been Design’d by Nature in the Construction of the whole Animal.
Secondly, Men sometimes erroneously Conclude, that such an Office cannot belong to such a Part, because they think, It is not so Commodiously Framed for it, as may be wish’d or devis’d; without considering, whether the Structure which they Fancy would do Better for that Particular Use, would not, in some Other as considerable Regard, Oppose the Welfare of the Animal: Or, whether it would be consistent with the Other Uses design’d by Nature in that sort of Living Creatures. For in the Living Works of so Excellent an Ingeneer as Nature, it must not be expected, that any Particular End should be prosecuted to the Prejudice of the Whole; but rather it must be suppos’d, that She Aims not only at Particular Expedients, but Universal Symmetry; and does indeed excellently Fit the several Parts, for their respective Offices; but yet only as far forth as a due Regard to the Design and Welfare of the Whole will permit. The Reasonableness of this Observation, One need but be moderately Exercis’d in Zootomy (as That is distinguish’d from Androtomy) to discern. For, tho’ Man be confess’d to be the most Perfectly Fram’d Animal in the World; yet, His Body is not made the Model, on which Nature has Fram’d the Correspondent Parts of Other Animals. The Lungs of Dogs, of Birds, of Frogs and Vipers, and I know not how many Others, are of a Structure very differing from Those of Man. He is not furnish’d with so many Stomachs as an Oxe or a Sheep, because Nature Intended not He should Ruminate like Them. Tho’ His Gall be lodg’d in a peculiar Bag, so Plac’d in the Liver, as to give Helmont a colour to call it Nucleus Hepatis; yet ‘twere unadvis’d to say, That the Secretion of Gall is none of the Uses of Those Livers, wherein Such a Cystis is not to be met with: Since in Some Amals, as in Horses and Pigeons, that Bitter Humour, (which in Frogs I have often oberved to be of a Deep and Transparent Green,) is not usually, as in Man, collected into one Bag: And in Vipers, tho’ it be included in one Cystis, yet, as far as I have observed, That Bag does not at all touch the Liver: And store of such Instances may be met with among the Remarks of Zootomists: Wherefore I pass on to Observe,
That, in the Third place, ‘Tis Difficult to Determine the True and Primary Use of a Part, because Nature does often Fit One Part for Several Uses. To which I shall add,
In the Fourth place, That the Difficulty is sometimes Increas’d, because Nature may compass the Same End by Several Means, each of them Sufficiently, tho’ not Equally, Commodious. I joyn these Two together, because in Effect they do often Concur, in making it Difficult to determin the True Use of a Part. And the latter of the Two is sometimes Increas’d by this, that Nature does not as Constantly, as some Men presume She does, Imploy only one Part to perform such an Office; but the Intended Effect is sometimes produc’d by a Series of successive Operations, to which several Parts may in Differing manners Contribute.
And here I observe, (what perhaps has not been Consider’d,) that neither the Mechanism of a Human Body, nor that of very Considerable Parts of It, is to be judg’d of, only by the Structure of the Visible Parts, whether they be those Solid or Stable Ones that the Anatomist’s Knife is wont to expose to Sight; or even by the Texture of those Fluid Ones, which are to be found in the Vessels and Cavities of a Dead Body when Dissected, tho’ never so Skilfully. For I take the Body of a Living Man to be a very Compounded Engine, such as Mechanicians would call Hydraulico-Pneumatical: Many of whose Functions, (if not the Chiefest,) are perform’d, not by the Blood and other Visible Fluids barely as they are Liquors; but partly by their Circulating and other Motions; and partly by a very Agile and Invisible sort of Fluids, call’d Spirits, Vital and Animal; and partly perhaps, (as I have sometimes gues’d,) by little Springy Particles; and perhaps too, by somewhat that may be call’d the Vital Portion of the Air; and by Things Analogous to Local Ferments: the Important Operations of all which are wont to Cease with Life, and the Agents themselves are not to be Discern’d in a Dead Body. So that, besides those Manifest Uses, which the Visible Fabrick of the Engine may suggest to an Anatomist; there may be Chymical Uses (if I may so call them) of some Parts, that serve for the Elaboration of Spirits and other Fluids: Which Uses, (as ‘twas formerly Observ’d, and yet ought to be Inculcated,) are not suggested to the Anatomists, as Such, by the Inspection of the Structure of the Parts; but to Discern them may require no mean Skill in Spagyrical Principles and Operations.
Such Considerations as the foregoing, make me think it more difficult than many do, to determin with any certainty the Main Use of divers Particular Parts, [for in some Others it seems manifest enough;] especially if it be done with the Exclusion of Other Uses. Nor is it enough, to Secure us that we know the Chief Function and End of a Part, to Know that it is contrived for such a Purpose. For upon the things I have lately represented, One may ground this Answer, that this Fitness hinders not, but that the Primary Use of the Part may be another, (as not Anatomical but Chymical, or Vice Versa,) more Conducive to the General Welfare of the Animal, or else to the Cosmical Ends of Nature. And it ought not to seem Strange, that some Pieces of Workmanship, that consist of many Parts, all of them Curiously Contriv’d, may by One Learned Man be guess’d to be Intended for This Use, and by Others for That Use, and yet Both these Uses may be worthy of the Artificer.
When some very Politick Prince does some Great Thing, without declaring Why; the Guesses of the States Men are often very differing, whilst yet none of them ascribe to Him a Design mis-becoming a Wise Man. And so, when a Learned Author Expresses himself, as sometimes it happens, Ambiguously, tho’ One Reader Interprets his words to This Sense, and Another to That, yet Both the Senses pitch’d on, may fairly comport with the Context, and the main Scope of the Writer. These things, I say, because I would by no means Disparage the Wisdom of Nature, by proposing the Difficulties I have hitherto mentioned; tho’ I confess, that, upon the account of These and some Others, I look upon many of the Arguments that several Authors have made bold to draw from Final Causes, but as Conjectural Things. And in divers Cases, I allow what is suggested to me upon the Supposition of the Intended Uses of Particular Parts, rather as good Hints to Excite, and give some Aim to, a Severer Inquiry, than as safe Grounds to build Physical Conclusions on.