PHYSICS. the fame kind. For by thus easily attaining to the knowledge of things, the mind gratifies, at once, both its vanity, and its lazinefs; looking upon these conclufions, as marks of the excellency of its rational faculty, whilft they rather proceed from a want of the due exercise of it.

The internal

mind.

But, fince there is no progrefs ad infinitum in the Criteria of truth; and light of the fince our faculties are the best inftruments that God has given us, to difcover, and to examine it by; I think, a clear light, or evidence of perception, fhining in the understanding, affords us the greatest affurance we can have, in a natural way, of the truth of the judgments we pafs upon things. And, it is not by induction, but by evidence, that we know nothing but truth follows from truth. By which it appears, that the innate light of the rational faculty, is more primary than the very rules of reafoning; fince, by that light, we judge even of this axiom, which is itself the grand principle of reafoning by inference. And, as the understanding is usually look'd upon to be the eye of the mind, there is this analogy between them, that there are fome things which the eye may difcern mechanically, or by the help of inftruments; as when it judges a line to be ftrait, by the application of a ruler to it, or to be perpendicular, by the help of a plumb-line; or a circle to be perfect, by the help of a pair of compaffes: but there are other things which the eye perceives and judges of immediately, by intuition, and without the help of organs, or inftruments; as when, by the bare evidence of the perception, it knows, that this colour is red, and that blue; that fnow is white, not black; and a coal, black, not white. For, thus there are fome things, which the intellect ufually judges of in a kind of organical way; that is, by the help of certain rules, or hypothefes, fuch as are a great part of the theorems, and conclufions in philofophy, and divinity; but there are others, which it knows without the help of these rules, more immediately, and, as it were, intuitively, by evidence, or perception; as that "two contradictory propofitions cannot both be true;" that "from truth, nothing but truth can justly be deduced," &c. 'Tis alfo, upon this evidence of perception, that we receive, with an undoubted affent, many primitive ideas and notions; fuch as thofe of extended fubftance, or body; divifibility, or local motion, a ftrait line, a circle, &c.

And, it seems to me, that the internal light, which the author of nature has fet up in the mind of man, qualifies him, if he makes a right use of it, not only to apply, the inftruments of knowledge, but also to frame, and to examine them. For, by the help of this light, the understanding is enabled to look about, and both to confider a-part, and compare together, the natures of all kind of things; without being neceffitated to employ, in its fpeculations, the rules, or dictates of any particular fcience, or difcipline; being fufficiently affifted by its own light, and thofe axioms and notions that are of a general nature, and perpetual truths; and fo, of a higher order than the dictates or rules of any particular, or fubordinate fcience, or art. And, by these means, the understanding may perceive the imperfection and falfity of fuch rules, or theorems, as thofe men who look no

Higher, nor further than their own particular science or art embrace for PHYSICS. certain and unquestionable. Thus, philofophers obferving that they could frame a clear notion of a thing, without confidering whether it were actually in being or not, or even when they supposed that 'twas not actually in being; as we can frame a clear conception of a rofe in winter, when there are none to be found growing; and have a notion of a myriagon, tho' very likely there is no fuch figure really exifting in the world; men have generally concluded, that the effence of things is different,*and feparable from their exiftence: yet when we confider that God is a Being infinitely perfect, and that actual exiftence, being a perfection, must belong to him; we may, by the fame light of reason that dictated effence and existence to be two feparable things in all other Beings, difcern, that they must be infeparable in God, and confequently that the foremention'd rule, tho' more general than almost any other, is not abfolutely univerfal, but must be limited by the light of reafon. And thus, alfo, philofophers confidering that not only all forts of bodies, but the immaterial fouls of men, are endow'd with qualities, which are accidents, have included it in the very notion of a fubftance, to be the fubject of accidents. But the free intellect, finding in itself a notion of an abfolutely perfect, and, therefore, exiftent Being; and confidering that to be the fubject of accidents, is not a thing agreeable to the highest perfection poffible, it concludes, that in God there are no accidents. And this conclufion has been embraced as: a part, not only of chriftian, but of natural theology, and maintain'd by feveral philofophers themselves, upon metaphyfical and other merely rational grounds. In fhort, the native light of the mind may enable a man, who will make a free and industrious ufe of it, both to pass a right judgment of the extent of those very dictates that are commonly taken for rules. of reafon, and to frame others on purpose for privileg'd things.

5thly, Where privileg'd things are concern'd, we are not bound to re- A fifth rule. ject as falfe whatever we know not how to reconcile with fomething that is

true.

I think it will not be doubted that there are, or may be conceiv'd, ftrait lines, whereof one is a hundred, or a thousand times longer than another; 'tis alfo generally granted, that a longer line confifts of, or may afford more parts, than a fhorter: and, laftly, 'tis generally acknowledg'd, that no number can be greater than infinite. Now I fhould gladly fee thefe propofitions reconciled to the demonftrations of geometricians, about the endless divifibility of all ftrait lines; whence they deduce, that tho' they be very unequal among themselves, yet the shortest of them contains, or may afford, infinite parts. I am far from affirming that one truth can really contradict another; yet I think that which is but gradual, or limited truth, may, in fome few cafes, be irreconcileable by us to an abfolute and univerfal truth. We may diftinguish those propofitions we call true, into axioms metaphyfical, or univerfal, that hold in all cafes, without reserve; and axioms collected, or emergent; by which I mean fuch

as

PHYSICS. as refult from comparing together many particulars that agree in fomething common to them all. And fome of thefe, tho' they be fo general, that, in the ufual fubjects of our reasoning, they admit of no exceptions, yet may not be absolutely, and without limitation, true. Of this we have an inftance even in that axiom which almost all natural philofophers have fupposed, and built on, that fomething cannot be made out of nothing; which tho' at least one of the highest or gradual truths, may yet not be univerfally true, fince for ought we know, God, who is acknowledg'd a Being infinitely perfect, may poffefs, and have exercis'd the power of creating. And, in fuch cafes as this, not to be able to reconcile a truth concerning a privileg❜d thing, with a propofition that generally paffes for true, will not presently oblige us to reject either propofition, as false; but, fometimes, without destroying either, only to give one of them a due limitation, and reftrain it to those forts of things on which 'twas at first grounded, and to which 'twas, because of man's ignorance, or inconfideratenefs, not at first confined. And if the miracles vouch'd for any religion, be any of them granted true, it cannot well be denied that phyfical propofitions are but limited, and fuch as I call collected truths; being gather'd from the fettled phenomena of nature, and liable to this limitation or exception, that they hold, only where the irresistible power of God, or fome other fupernatural agent, is not interpos'd, to alter the course of

nature.

Now the reason why we judge things are repugnant, being, that the notions or ideas we have of them feem to us inconfiftent; if either of these notions be wrong framed, or be judg'd of by an unfit rule, we may think those propofitions to be contradictory that really are not. Thus those used to employ their imaginations about things, which are the proper object of the intellect, are apt to pronounce others to be inconceivable, only because they find them unimaginable; as if the fancy, and the intellect, were faculties of the fame extent. Upon which account, fome have fo grofly erred, as to deny all immaterial fubftances, and chofe rather fo far to degrade the Deity itself, as to impute to it a corporeal nature, than to allow any thing to have a being, that is not comprehenfible by their imagination, which themselves acknowledge to be but a corporeal faculty. But befides this mistake of things repugnant, which arifes from the mifapplication or mifmanagement of our difcerning faculties, there may be another that proceeds from the imperfection and limitation of our understanding; which being unable to judge of privileg'd things, as it does of other objects, may fometimes be unable to difcover the reconcileableness which

more illuminated and penetrating faculty may difcern. This may be illustrated by what ufually happens at fea, where there is a free profpect; when, looking towards the main, the sky and the waters feem to meet at the edge of the fenfible horizon; tho', indeed, they are as far diftant, as the heavens from the earth. On the other hand, if you skilfully mix together the dry and fine powder of orpiment, and that of indigo, you will produce a green colour, as is known to painters; where

in the eye takes notice but of an uniform mixture, in which it diftinguishes PHYSICS. neither blue nor yellow; but if you look on this mixture thro' a microfcope, the former colour difappears, and you will plainly fee, inftead of it, blue and yellow grains of the powder, diftinct from one another. These inftances may ferve to fhew the weakness of our vifive faculty, and the latter of them teaches, that a thing may appear one and different, as 'tis look'd upon by a more or lefs difcerning eye. But an inftance more to our prefent purpofe is afforded by yellow diamonds, which, because of their colour, the generality of goldfmiths take to be counterfeit gems; tho' very skilful lapidaries will, by fure figns, difcover and acknowledge them to be true diamonds. Whence we learn, that a more skilful judge may difcern an agreement in things that almoft all other men think they fee manifeftly to be of different natures.

I have alfo feveral times obferved, that men judge two things to be irreconcileable, not only when they are both of them reprefented to the understanding in the form of propofitions, but when one of them is only a notion, or a current definition. For feveral of these notions contain in them a propofition, or are equivalent to it: as, when a circle is defined to be a figure contain❜d by a line, all whofe parts are equally diftant from a point in the middle; this definition contains an affirmation of the effential property of a circle, which by the generality of geometricians is therefore diftinguifh'd from that conic fection they call an ellipfis, tho that be alfo a figure terminated by one curve line.

But if a man has not genuine and adequate notions of the things he judges of, he may confidently, and even upon very probable grounds, take things to be inconfiftent, that in reality are not fo. If an ordinary mathematician fhould hear one man fay that fuch a figure is an ellipfis, and another affirm it to be a circle, he would think their affertions to be inconfiftent, having his mind prepoffeffed with an ellipfis being a conic fection, whose properties must therefore, be fuppofes, be very different from thofe of a circle; whereas fuch wary geometricians as the learned Dr. Wallis, will tell him, that the vulgar notions of conic fections are not adequate to the figures producible by them. 'Tis true, when a right cone is cut quite thro' by an inclining plane, the figure produced by the fection agrees well with the receiv'd notion of an ellipfis, in which the diameters are of an unequal length; yet if the plane cut the cone parallel to the bafis, that conic fetion will be a true circle, having all its diameters equal.

'Tis indeed an uncommon and unheeded account, but fuch an one upon which I have obferv'd not only logicians, but philofophers themfelves, to err about judging things reconcileable, or inconfiftent; that if a man be not fufficiently acquainted with the nature of either of the two things under confideration, he may think there is a contradiction between them, when there is none to a fuperior understanding. For taking it for granted that he knows one thing for a truth, if fome other thing be affirm'd to be fo, which he has not skill enough to fee how to reconcile to

the

PHYSICS. the other; no wonder, how well foever this may be evinced, that he should as little know how to admit, as how to reject it. Thus, a novice in arithmetic, for example, finding that, according to his rules, there is not one mean proportional number between 4, and 32, will scarce be able to reconcile that propofition to this other, that there are two mean proportionals between the fame numbers; for he may, with a great appearance of reason, ask how, if there be not fo much as one mean proportional, there can be two? whereas, those who are acquainted with the nature of ranks, or series of numbers, proceeding in geometrical proportion, will easily dif cern, that between thofe two, both the number 8, and the number 16, are proportionals. Thus, if an old fchool-philofopher, or a mathematician, not acquainted with the later difcoveries made by telescopes, fhould hear one man fay, that the moon is the moft enlighten'd when the appears full to us; and another affirm, that he is more enlighten'd at the new moon than at the full he would readily conclude, upon the fuppofition that the moon receives all her light immediately from the fun, that the latter affirmation cannot be true; which, yet, he would not conclude, if he knew that the moon is as well enlighten'd by the earth, as the earth by the moon: upon which account, as at the full the receives but those rays that come to her directly from the fun; at the change, fhe receives both them in that part of her body turn'd to him, and those other beams of his, which are reflected from the terreftrial globe to that part of the moon that is nearest to us. And thus, alfo, before the time of Pythagoras, not only the vulgar of the Greeks, but their philofophers, and mathematicians too, often obferving, that a bright star preceded the rifing fun; and that, frequently, likewife on other days, after fun-fet, another ftar appear'd, which was none of the fixed ones; they, confidently, concluded, from the diftant times of apparition, that the fun was attended by two different ftars; to which, accordingly, they gave two different names: but Pythagoras, (who was a far better aftronomer, as appears among other things, by his maintaining, in those early times, the motion of the earth about the fun) undertook to difabuse them, and effected it. Now, if one who had observ'd Venus, only in the morning, fhould have affirm'd, that, befides the fix known planets, there was a feventh, Phosphorus, which preceded the rifingfun; and another, who had taken notice of her only in the evenings, fhould affert, that, befides the fame fix known ones, the only feventh was Hesperus, which, fometimes, appear'd after his fetting; aby-stander would presently have concluded, that their affertions were not reconcileable, either to one another, or to the truth; which, in his judgment, was, that there must be no less than eight visible planets. Yet Pythagoras,, who had more skill, difcern'd, and taught, that these two phenomena were produced by one and the fame planet, Venus, determin'd, by its peculiar motion about the fun, to fhew itfelf near our horizon, fometimes before he afcends it, and fometimes after he had left it. Such inftances as thefe, tho' offer'd but as illuftrations, may diffuade us from being too forward to reject every propofition that we fee not how to reconcile to what we