Part 6

LVII. The second argument, is built on the correspondence of the four humours of the body, with the four Aristotelic elements; that is to say, the blood with the air, the choler with the fire, the melancholy with the earth, and the pituitous with the water. But this puts us in a worse situation than we were before. In the first place, it is a doubt among the medical people, whether the humours of our bodies consist precisely of four. Some say they are more, and others that they are less. Some add to the four, the lymph, the pancreatic juice, and the nervous fluid; and some again will not admit, that there is any other humour except the blood. Secondly, if the four elements correspond only with the four humours, we are left without an element to correspond with the solids, which on account of the hardness of their substance, might with more propriety be compared to the earth, than to the melancholy humour, which is beyond comparison less hard and solid than the other. Thirdly, in the same voluntary manner, with which they assign four elements to correspond with the four humours, they may assign one element to correspond with the flesh, another with the bones, another with the marrow, another with the fat, or adipose substance, another with the tendons, and so on. Fourthly, in order to reason justly upon the human body, or animal species, we should not seek for four substances that are analogous to the four humours, but for four that enter into all the mixtures; for the question, relates to elements that partake of the composition of all mixtures in general, and not precisely of the animal. But what traces can we discern, of four humours, or four substances, equivalent to these, either in minerals, or plants?

LVIII. The third argument in support of this quaternian system, is pretended to be derived from experience; for it is alledged, that when a piece of wood is burning, we see it resolve itself into the four Aristotelic elements. At first it emits a small portion of water; then it takes fire; the fire is followed by smoke, which we know to be of an aerial nature, by its ascending to the airy region; and last of all, there remains a portion of earth in the ashes.

LIX. Although as Etmuller says, in matters of physics and medicine, _præstat unum experimentum centum rationibus_, still, the experiment just alledged is so defective, that it is not of more value than the arguments before urged. In the first place, dry wood, may as properly be called a mixture as green wood, notwithstanding which, it emits no water upon being laid on the fire. Secondly, as we are here treating of the elements in general which enter into, and make a part of the composition of every species of mixture, the fire should produce the same appearances, and have the same effect upon them, that it has upon the wood; but this does not happen, for minerals laid on the fire emit no water, unless it is when they have imbibed some foreign moisture. Thirdly, the chymists by means of fire differently applied, extract from wood and other mixtures, various substances, which differ from those four that are produced from the wood in the ordinary way of burning it; and it seems reasonable from hence, that we should augment the number of the elements. Fourthly, we do not know whether these substances pre-existed in the wood, or whether they were produced _de novo_ by the fire. Fifthly, the ash is not earth, nor an elemental or simple body as is supposed, for there may be separated from it a large portion of salt, which is a distinct substance from either of the four; for it is neither earth, air, water, or fire. Sixthly, neither is the smoke air, as is manifest from the soot which condenses in the chimney. If I should be told, that in the smoke is contained a variety of particles, some of which compose the soot, which remains in the chimney, and others which mount higher, and are impregnated with the atmosphere, and become air; I reply, that in consequence of this, they should admit of a fifth element of soot; or to speak more properly, of five or six additional elements; for Mr. Boyle informs us, that the chymists can extract from soot, five or six different substances. Finally, all that becomes ashes, existed before in the form of fire; from whence it follows, that the form of ashes is a new production, for matter cannot exist under two substantial forms at one and the same time; and consequently, the elemental form of earth which the Aristotelites ascribe to the ashes, could not pre-exist in the mixture, but must be a new production. This objection militates principally against the Aristotelic principles; but others might be formed in different shapes, against every system whatever.

LX. I have combated only the Aristotelic opinion of the elements, not because the others are not incumbered with equal difficulties, and exposed to equal objections, but because in Spain, we suppose the others to be perplexing, and even improbable, and conclude that of the four elements, to be just and right; I therefore chose to attack this system, to let my countrymen see, that we know nothing with certainty respecting the elements.

SECT. XIV.

LXI. I have remarked before, that if we are ignorant of what the elemental bodies consist, we cannot possibly know the nature of the mixtures. But even if we could ascertain what the elements are, we should still remain in profound philosophical ignorance with respect to the component parts, of both them and the mixtures; for admitting the four following, air, fire, water, and earth, to be elements of all the mixtures; who has yet ascertained the nature of those four bodies? Aristotle only reasoned upon their qualities, and this he did with so little precision, that all he said may be looked upon as doubtful, for he had no solid principle, from whence he inferred, that they possessed the properties which he attributed to them; but drew all his conclusions, from an ideal proportion which struck his own imagination; and respecting which, it has since been proved, that he was mistaken. He says that air is hot, and fire dry in the highest degree; but in our essay on physical paradoxes, we have proved that the air is not hot; and according to Aristotle’s definition of humidity, we may infer, that a flame is humid, for it cannot be contained within its own bounds, but pervades other regions. We also proved in our essay on physical paradoxes, that elemental fire is not hot in the highest degree; and to what I said there, I will add in this place, that experience shews us, one fire is hotter than another, and has greater power to heat or melt substances, either in consequence of its greater bulk, or on account of the matter with which it is made, or the manner the place is disposed and contrived, in which it is lighted; from all which it may be inferred, that fire in its nature is not hot in the highest degree, for if it was, as in every fire the nature of fire is preserved, every fire would be hot in the highest degree, and of course, could not be exceeded in heat by another fire.

LXII. Aristotle however, did no more than assign false or uncertain qualities to his four elements, and left untouched, substantial nature which is the root of them; and those who succeeded him in all after-ages, if they aimed at more, attained no more. The sectaries of Aristotle content themselves with saying of the elements, what they say of all other natural compositions; that is, that they are constituted of matter in physical forms, are real incompleat entities, and evidently distinct from each other. By all which, admitting this description to be right, they teach us nothing, till they explain to us, of what the physical form consists, and what is the specific nature of the physical form, in every natural composition. But their system explained in the general way, in which they themselves define it, is strongly combated by the modern philosophers, who find an insurmountable difficulty in the generation of the material forms, not being able to comprehend, how their production can be any thing else but a new creation; for the arguments the Aristotelites fly to, of deducing them from the power of the matter, contain nothing but words, void of all real signification; and truly Aristotle himself having said, that the form is one of the principles of a natural entity, and that the principles are those things, which are neither made from their own substance, nor from that of any other entity whatever, shew them to be words which have no fixed meaning: _Quæ nec ex se, nec ex aliis, sed ex quibus omnia fiunt_; how then can we reconcile this doctrine, with the form being made of the matter?

SECT. XV.

LXIII. But have the moderns who exclaim so much against Aristotle, hit upon the truth? By no means. They have reasoned more boldly, but not with better success. They tell us, that the texture, collocation, figure, and motion of the particles, produce all the operations of nature, without the necessity of having recourse for this purpose, to accidental or substantial forms; but by saying this, they expose themselves to the same fault which they reprehend in the Aristotelites, which is that of speaking too generally; for as these last, do not explain or define, of what the substantial form consists which distinguishes one entity from another, neither do the others determine, the texture, co-ordination, and figure of the particles which appertain, and are proper to each composition; in consequence of which, they all involve themselves in innumerable difficulties, which they reciprocally object against each other. The Cartesian system appears chimerical to the Gassendists, and the Maignanists; and these two last parties, although they agree in assigning the Atoms as the principles, and elements of all material things, oppose one another in various particulars, it being a principle with the Maignanists, that the Atoms are different in species, and with the Gassendists, that they differ only in figure; all of which systems, are exposed to be combated by arguments that are terribly strong.

SECT. XVI.

LXIV. From all that has been said, it may be evidently concluded, that we know nothing of the nature of that principal object of physics, _an ens mobile_, either taken as confined to individuals, or considered with respect to the species, or contemplated in an abstracted sense, as relating to the gradations, of lowest, inferior, or supreme. What one sect affirms, another denies, and the worst is, that, attend to the reasoning of which of them you will, you will find the arguments against the system of each, stronger than the proofs in favour of it. On this account, Lactantius said wisely, that philosophers have swords, but no shields: _Gladium habent, scutum non habent._ They produce penetrating arguments wherewith to assail the opinions of their opponents, but not solid solutions, wherewith to defend their own. What can we do then in such a case? Why nothing but suspend our judgment, till some angel shall decide the contest.

LXV. Perhaps some one will remark to me, that the substantial nature of things is at a great distance from our view, and that therefore it is not wonderful, that we have not yet penetrated into the inmost recesses of philosophy; for that without advancing so far, we may find sufficient matter whereon to exercise our speculations, in contemplating the ordinary phenomena of nature, and by endeavouring to discover their proximate causes; which attempt, may possibly be crowned with success, by observing and reasoning upon every species of movement which is performed by an entity, that has motion or circulation, according to the nature of such an entity.

LXVI. I will acknowledge, that philosophy helps us to reason upon natural phenomena, and to enquire into their more immediate causes; but in doing this, we frequently wander in the dark, and are much exposed to be interrupted by impediments, produced by ignorance and doubts; except it is in the case of a few truths, the discovery of which, we owe to the light of experience; and this fact is evinced, with respect to the very instance of motion which has been just alledged.

LXVII. With regard to the movements of generation, corruption, alteration, augmentation, and the rest, which are considered as distinct from local motion, you can find nothing that is not questionable, both in the schools of the Aristotelites, and in those of the modern philosophers. The very definition of motion in general, which was given by Aristotle, some reject as obscure, others as perplexed, and others as nugatory. The movements we are now treating of, in the opinion of Aristotle, are acquisitions of new forms, either substantial, or accidental; but the Moderns, who deny the existence of all material forms, object to this definition of those movements. Even among the Aristotelites themselves, it is not agreed, whether motion is not influenced by passion; nor whether the first, is not obedient as a passive agent to the last. And thus in every thing else, it is all question, and all dispute.

SECT. XVII.

LXVIII. And why should we be surprized that with respect to these movements, which as we may say, nature executes behind the curtain, human understanding has made so little, or next to no advances? what we ought more to wonder at, is, that it happens the same with respect to all local motion, which lies so plain and open to our observation.

LXIX. The motion with which heavy bodies descend, is the most frequent and common to our view. And what do we know of this? Of its properties very little; of its causes nothing. We know it acquires some degree of acceleration in its passage, because we see it; but what is the proportion of the increased acceleration, is matter of great debate, both among the philosophers, and mathematicians. We know that it is a motion of descent, but we do not know whether its course is directed to the centre, or the axis of the earth. The cause of this motion remains so hidden, that the philosophers to this day, have given no opinion concerning it, that I will not venture to pronounce an absurd one. The Aristotelites, by saying the cause of this motion proceeds from an innate disposition to move in every thing, say nothing, unless they point out the particular virtue or faculty, which excites motion in heavy bodies, for what we have just mentioned, is the reason they generally assign for all species of movements. They should not be allowed to dispute or controvert what they themselves have advanced; and if they should attempt to give a more rigorous definition of their opinion, they would fall into a still greater absurdity; which made the learned Father Saguens say, _Quis non palpat crassitiem hujus chimericæ opinionis?_ The Cartesians to account for this phenomenon, recur to the vertical motion of the subtil matter, which separating itself from the earth, and pursuing the angle or direction of tangents to the circle, impels heavy bodies to descend. But this reasoning has been confuted by most efficacious mathematical arguments. Gassendo invented an effluvia composed of terraqueous corpuscles, which mount into the air, and penetrate the pores of heavy bodies, which they generally encounter, and after turning their first course into a descending one, impel them downwards. Nothing has so much convinced me of the great difficulty of this question, as seeing a man of the subtil ingenuity of Gassendo, recur for the solution of it, to a fiction destitute of all probability; and which is exposed to invincible objections. Father Maignan, and his followers also, make use of the terraqueous effluvia for the solution of this difficulty; they do not allow that they act by impulse, but that by their sympathetic and magnetic virtue, when they come in contact with heavy bodies, they dispose them to descend.

LXX. It is very probable, and perhaps more than probable, that the ascent of light bodies, is caused by the descent of heavy ones; because the heavy body has power, in consequence of the impetus of its descent, to occupy the lower station, where meeting with the light body, it obliges him to leave that situation, and to mount upwards; for many argue with great colour of reason, that there is no such thing as absolute lightness to be conceived in any body whatever, nor is such a quality necessary, a respective or comparative lightness, being sufficient to answer every purpose. Thus we say a body is light, not because it is void of gravity, but because it is less heavy than the one with which we compare it. In the same manner we say the air is light, not because it is not ponderous, but because it is less so, than earth, water, and all the other bodies that surround us; and that no other levity but the respective, is necessary to cause bodies which we call light to ascend, may be clearly seen in the case of oil, which notwithstanding that it is heavy, if you pour a quantity of water into the vessel where it is, the water on account of its superior gravity, will occupy the inferior station, and oblige the oil which was at the bottom to ascend. The same thing happens with regard to air. If you dig a ditch to any depth in dry ground, the air will descend and occupy the whole of it; and there is no other way to dispossess the air from the bottom, and to make it rise upwards, but conveying water into the ditch, or by throwing into it some body that is heavier than the air.

LXXI. It is not owing to the principles of physics, but to experience, that we understand the little we know of this matter; and with respect to this little, there still remains great difficulties for philosophers to contemplate; and the greatest of all, is ascertaining the cause of the ascent of vapours to the region of the air. It is certain, that vapours are nothing else but water, resolved into exceedingly minute particles. The water however being heavier than air, how can the water arise to the height occupied by the clouds? Every particle of water notwithstanding it weighs very little, is much heavier than a particle of air of equal size, and the greater or less gravity of liquids, for the purpose of their impelling one another, is computed in the gross, and not according to the proportion of globules of equal size; and we know that a pound of water, will cause a quarter of an hundred of oil to rise in a vessel.

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?