Part 7

LXXII. Some philosophers, who were aware of this serious difficulty, upon reflexion, conjectured that some portion of ethereal matter or pure air, might adhere to each particle of vapour; and in consequence of this conjunction of the two, the whole might become lighter than an equal quantity of the inferior gross air of our atmosphere; and on this account, might mount on the top of it; for although iron is much heavier than water, if we fasten a small portion of iron to a bit of deal board, it will swim, because the quantity of iron and board together, is lighter than an equal bulk of water. Francis Bayle, adopts this opinion of a portion of the ethereal matter adhering to the vapour; and on the other hand, Father Pardies a French jesuit supposes, that a particle of extended vapour, in the form of an air bubble, contains in its cavity the ethereal matter. All this is far from certain; but I shall not detain myself in controverting, either the one or the other of these modes of reasoning. Others again imagine, that various igneous particles, which arise from the earth, after separating from the water or some other liquid those small particles which we call vapour, with their continual impulse and agitation, force them upwards. But neither does this system appear to me very defensible, any more, than that of the vulgar philosophers, who say, the sun by its activity attracts the vapours; for if this was so, the vapours would not stop till they reached the sun, or at least till they were obstructed in the heaven of the moon, by the moon itself, or some other solid body; for the attractive power is stronger, the nearer the thing attracted advances to that which attracts it; and the first would never cease to move towards the other, till it came in contact with it, if it was not interrupted in its course by some obstruction; and besides, the attractive virtue is a certain something, which nobody can comprehend, and is therefore in a manner wholly banished from philosophy.

LXXIII. Who would not be surprised, that physics should not have helped us to attain a knowledge of so common a phenomenon, as that of the ascent of vapours? but so far has it been from attaining it to any degree that comes near to truth or certainty, that hitherto, we have not been able to discover any thing upon the point, that is satisfactory to the understanding. And with respect to all other species of motion, we are in the same predicament.

SECT. XVIII.

LXXIV. Have we attained a knowledge of the cause of the elastic motion, which is the property that makes a wand or a sword-blade which is forcibly bent, recover of itself, the straight form it had before, or if it was naturally bent or crooked, and was opened and made straight by force, makes it return to its original crooked shape? Descartes, for the explanation of this phenomenon, recurs to his common asylum, the impulse of the subtil matter, which not being able to penetrate the pores of the wand or sword-blade on the hollow side, where the pores are closed by the inflexion, by its great efforts to open and penetrate them, causes the wand or sword-blade to recover its former figure. But who does not perceive, that for this purpose, it will be necessary to suppose the subtil matter should be for ever moving in opposite directions, from west to east, and upwards and downwards, &c. for the wand or sword-blade, to whatever aspect you turn the hollow side, recovers its natural figure equally the same? Besides, Descartes supposes the subtil matter to be infinitely fluid, from whence it follows, that it will be impossible to shut the pores in such a manner, as that they will become impenetrable to it.

LXXV. Others say, that the same impulse which is impressed on a wand or bow by him that bends it, is the thing which opens it afterwards. But against this opinion, it may be urged in the first place, that he who bends it, does it gradually and by slow degrees; and the impetus with which it opens, is violent and quick. Secondly, the archer who bends a bow, is not possessed of a force equal to that, with which it reverts to its former figure, for that is so great when the arrow is drawn near the head, that it is capable of giving it an impetus, that will pierce a substantial thick body through and through; and how can any one communicate a force or impulse, which is greater than that he possesses?

LXXVI. The Aristotelites, who are great adepts at the easy invention of giving the name of quality, virtue, or faculty, to express the cause they are enquiring after, and by the addition of an adjective to that name, which is a denomination taken from the effect, say, that the cause of the elastic motion, is an elastic virtue which is inherent in the wand or sword-blade. This is in reality, having found out a master key, to unlock all the mysteries of nature; for there is nothing so obscure, that with this invention may not be made manifest. If you ask, what is the cause of the marvellous properties of the load-stone, the answer is, the magnetic virtue; if you ask, what are the causes that perform in us the operations, of the concoction of aliments, the expulsion of excrements, and that of nutrition, &c. the answer is, that they are performed by a concoctive virtue, an expulsive virtue, and a nutritive one; and according to the same mode of reasoning, the cause of the winds, is a ventilating virtue, that of lightning a fulminating one, and that of the flux and reflux of the sea, is owing to two opposite virtues, the one fluxive, and the other refluxive. By this cheap mode of philosophizing, every thing is demonstrated at a glance. But to speak seriously, what is this, but answering in the very language of the question? Saying that the cause of the elastic motion, is the elastic virtue, is in effect the same as saying, the cause of the elastic motion, is the cause of the elastic motion; and saying the magnetic virtue, is that which causes the load-stone to attract the iron, is answering in the stile of pleasantry, which some children have studied, and are very ready at; who when a person asks one of them, _My lad, whose son are you? the boy answers my father’s_.

SECT. XIX.

LXXVII. The cause of the progressive motion, is also very difficult to be accounted for. It is hard to comprehend, how the motion of a stone thrown from the hand subsists, after the action of throwing it ceases. Who moves the stone after the hand is still? What many of the Aristotelites say, is, that the action of the hand produces a quality in the stone, which they call impetus, and that this quality causes the stone to move after it is thrown from the hand. But this solution, is destitute of all appearance of truth. If every violent motion, as the Aristotelites maintain, proceeds from an extrinsic cause, how can the motion of the stone thrown in a mounting direction, which is a violent one, proceed from an intrinsic quality communicated to the said stone? If all generation, or accumulation, according to the doctrine of the same school, supposes corruption, what quality or accidental form in the stone was corrupted, to prepare it for engendering that new quality, which they call impetus? What dispositions preceded this generation? Or what time is there for their preceding it, when a globe of great bulk, with its motion impels a little one? It being certain, that the contact of the two, does not continue longer than an instant, what property then has that quality, to occasion so quick a corruption? Is it perchance, the gravity of the stone itself? This however, as it subsisted at the time of receiving the impulse, if it is a property opposite to that quality, would at the instant, have prevented its generation, as it is afterwards said to impede its conservation. We might make many other reflexions, to prove, that that quality is chimerical. Others recur to the air, for the means by which the motion is continued, which they say, being violently divided by the fore part of the stone, takes a sudden turn to the hinder part, and impels the stone forward. But omitting many other objections, which would render this mode of philosophizing totally improbable, I shall just remark, that it would follow from hence, that a stone could not move through a void space, give it what impulse you will, which is what I imagine nobody can believe. Descartes, reconciles this difficulty, with his maxim respecting the general law of the communication of motion, established by the Author of nature at the creation, which we shall not combat minutely, in order not to waste time; but shall content ourselves with observing, that that maxim applied to the present matter, and throughly investigated and explained, would signify, that the stone thrown from the hand, moves because God has ordained that it should move; but to solve difficulties in this way, it is not necessary to study philosophy.

SECT. XX.

LXXVIII. Finally, there is no motion whatever, about the cause of which, the philosophers do not altercate. What contests have there been among them, to explain how the movements of rarefaction, and condensation are performed? Some fancy, that rarefaction consists, in the same quantity of matter occupying a larger space; which explanation, others looking upon as unintelligible, assert, it consists in the opening of the pores, and the extension in consequence of that opening, of various parts of the body, by the introduction of a subtil liquid substance, in the same manner that water enters a spunge, or as rarefied air enters water, or the ætherial matter insinuates itself into the air. This is the doctrine of the Cartesians; but in the opinion of the Maignanists, and Gassendists, such reasoning is nothing to the purpose; for these, as they admit in nature, not only of the possibility, but of the necessity of a vacuum, or many voids distributed in small interstices, find no inconvenience in supposing, that in bodies, there are small empty spaces, unpossessed by any matter whatever.

LXXIX. Fermentation, this solemn instrument of nature for the performance of an infinite number of her works; consists in nothing, but an intestine motion of the insensible particles of the mixtures, by which is solicited, a new combination of their elements. But from whence does this motion proceed? The Moderns, since the discovery of the acid and the alkali by Otho Takenius, attribute all the fermentations, to the meeting of these two substances. But this is only pointing out the matter, on which this motion has its effect, and we do not enquire here for the material cause, but for the efficient one. Who, or what, impels the acid and the alkali to this conflict? The juice newly expressed from the grape, will quiet this combustion for some little time; but after that, the tumult begins again. What new agent can we discover here, to excite the second fermentation? This is a secret, which only the Cartesians have presumed to unravel, by recurring to their invisible fairy, _the subtil matter_; whom they make the author of all this domestic sedition. It is with some propriety that I call it a fairy; for as the vulgar attribute to the fairies, all the nocturnal noises and commotions, whose causes they are ignorant of; so the Cartesians impute all those motions, which on account of the darkness that obscures their causes, may be truly termed nocturnal, to the impulse of the subtil matter.

LXXX. I am so far from believing, that the subtil matter is the _primum mobile_, or first mover of every thing, that I am inclined to think, it moves nothing. My reason for this opinion, is as follows. The more fluid a matter is, so much the less impulse it makes on any body it encounters. Thus we see, that water gives a much less violent shock to a wall, than any other solid body of equal size, that may be forcibly driven against it; and air, a much less than water. No building could stand against, or resist a moderate gale of wind, if the air was as solid as water. The subtil matter then, according to the doctrine of the Cartesians, being infinitely fluid, can have but little impulse, or be able to impress but little agitation or motion, on the bodies it encounters. This consequence to me, is clear and plain; because, if in proportion to the augmentation of its fluidity, the impulse of a body is lessened, when the fluidity comes to be infinite, the impulse will cease totally. From hence it would follow, that there is no body whatever, which could be moved by the impulse of the subtil matter.

LXXXI. But admitting that it has power, as the Cartesians pretend, to move the insensible particles of the mixtures; it will not follow from thence, that it furnishes us with an explanation of the present phenomenon. For in the first place, the subtil matter, if it has any impulse, exercises it on the particles of the juice the instant that it is pressed from the grape; and even perhaps did it before, while the liquor was contained within the outside skin or covering. How then does it happen, that it did not sooner excite that tumult, which is the symptom and property of fermentation? Secondly, how can the acids and alkalies be said to produce this effect? for, according to the doctrine of the Cartesians, of whatever particles the mixtures consist, the subtil matter would set them in motion, for that there is no mixture whatever, impenetrable to its extreme subtilty. Thirdly, how can those exceeding slow fermentations, which are years before they manifest themselves, as in the instance of treacle, be attributed to the rapid and swift motion of the subtil matter?

SECT. XXI.

LXXXII. Saint Austin says wisely, that what is most surprizing, does not seem to strike us, although it is the object of our daily experience; which is a maxim, the saint applies to the wonders of nature, and falls in exceedingly _à propos_ to suit with our present discussion. All the philosophers he observes, admire as portentous things, the flight of the iron to the load-stone, the pointing of this last to the poles, and the flux and reflux of the ocean. If we ask them why they consider these motions as wonderful, they will answer, it is because they cannot ascertain their causes. But we cannot help remarking, that this answer amounts to a virtual acknowledgment, that all the movements of nature are equally wonderful, with those of the iron, the load-stone, and the ocean, for their causes are equally disputed, because we are equally ignorant of them. The only difference between them is, that these motions are confined to particular or determined entities, and the others are common, or nearly common to all.

LXXXIII. I confess for my own part, that on whatever side I view nature, I equally wonder, because I find myself equally ignorant of it. The same Saint Austin, whom we have just quoted (Tract. 24. in Johan.), observes, that the ordinary multiplication of grain, which is obtained at harvest, by means of the fertility of the earth, is equally a prodigy, with that extraordinary multiplication of loaves and fishes, which was effected by the majesty of Christ in the desert. Let now the vain philosopher boast, that he is able to decipher that great mystery, only because he is possessed of a compleat apparatus of faculty phrases; such as _seminal virtue, previous dispositions, the corruption of one form, and the introduction of another, attraction of the nutritious juice, the conversion of it into the proper substance, vegetation, nutrition_, &c. Was Saint Austin peradventure ignorant of those phrases, or of others equivalent to them? Yet notwithstanding this, he looked upon that natural multiplication of grain, as an impenetrable mystery. These phrases, only express or describe those operations which are familiar and open to our experience; but do not reveal to us, their causes, or the manner in which they are performed. The rustics, are acquainted with many more terms than we, expressive of the various operations with which nature in succession, proceeds to perfect that work. Are they peradventure on this account great philosophers? what do I explain, by calling vegetation or nutrition, that progression, by which a plant acquires its increase in bulk? does this afford me any philosophical knowledge, respecting the manner in which that operation is performed? There are two principal things to be considered in vegetation; the first is, the ascent of the nutritious juice by the fibres of the plant; the second is, the conversion of this juice into the vegetable substance; and we perceive in those two things, two great mysteries. If we ask the school philosophers, how the nutritious juice which is ponderous, rises spontaneously to the very uppermost leaves of the highest trees, they will tell us that it rises by attraction. And what is this, but placing us in the same state of doubt and difficulty, with respect to the most common work of vegetation, that we remain in, with respect to the motion of the iron to the load-stone? Both the one and the other are called attraction, but we are equally ignorant, why, or how, the highest leaves of a tree attract the juice which rises from the bowels of the earth, as we are, why or how the load-stone attracts the iron.

LXXXIV. Let us proceed to the second mystery. Who can explain to me, the manner in which a juice that is so exceedingly fluid, subtil, and fine, as to be able to circulate through the smallest channels of the fibres, is afterwards converted into the solidity of wood or grain; and this difficulty will increase, if we cast our eyes on the other mixtures, and reflect, that from another juice, or rather most fluid vapour, is generated copper and marble. Aristotle had certainly some reason for saying, that nature was the very devil: _Natura dæmonia est, non divina_ (Lib. de Præsens. per somnum); for by observing her works with attention, it seems as if she did every thing by enchantment.

SECT. XXII.

LXXXV. It would be even some consolation to us under our ignorance, if only the manner, in which nature works in the interior part of her operations, was hidden from our eyes; but the most humiliating circumstance is, that it is the same, with respect to every thing that immediately presents itself to our senses. Bodies are familiar to our touch; but hitherto, we have not been able to discover, whether they are composed of indivisible points, or of parts infinitely divisible; nor to what it is owing, that one body is hard, and another soft, one solid, another fluid, one opake, and another diaphanous. We are continually viewing colours; but we do not yet know, what sort of things colours are; whether they are mere reflexions of the light, or whether they are intrinsic accidents appertaining to the object. The light illuminates, and assists us to see; but we find our understandings greatly obscured, when we consider the nature of light. Whether we conceive it to be substance, accident, body, or spirit, none of them are applicable to its nature, and still they all seem to be so. And with how many impenetrable doubts and difficulties are we surrounded, when we consider the species which we call visible? If there is any one difficulty superior to, or any one inequality more striking than another in the mysteries of physics, I will venture to pronounce this is it. How the visible species of a star in the firmament, can in an instant, be translated from the same star to our eyes, when it must travel in that instant many thousands of miles, is beyond conception; as is likewise, how this species can exist at one and the same time, in the whole immense space between this and the firmament; it being certain, that in all this space, there is not a point, from which, by taking the view, you will not see the star. How also, contrary to the maxim of Aristotle, can many material species, differing only in number, exist or be seen, from the same point of space; it being certain, that you may from such an identical point, see distinctly, many stars at the same time? I shall omit many other objections, that are not inferior or less forcible to these I have urged, against the common opinion, that might be also urged, against the mode of reasoning of the modern philosophers.

SECT. XXIII.

LXXXVI. So that we see, our philosophy, from what we call first principles, down to our ultimate conclusions, is nothing but a fabrication, or weaving together of fallible conjectures; and that even these conjectures, terminate in nothing more than certain general notions; for the nature of all the specific things, and the greatest part of the causes respecting the lowest species, are so far removed from our penetration, that we can hardly arrive at attaining a doubtful idea of them. If we hit upon a truth, we owe the knowledge of it to experience, and this cannot be called scientific knowledge; for it is derived from self-evident principles, which may be comprehended by the most stupid of mankind; between whose manner of explaining the matter, if they attempt doing it, and ours, there is only this difference, that we define it in terms of art, and they in ordinary and common ones, which are better than the others, because they are more intelligible. This made the learned Jesuit Claudius Franciscus Dechales say, that our physics consisted of nothing but a particular idiom, which conveyed no certain knowledge of any thing. (Tom. I. tract. de Progressu Matheseos).