Chapter III: Part 3

XLVIII. Besides this, some express a doubt, whether plants are vegetable or not; and some are also doubtful, whether the property of vegetation does not likewise belong to stones and metals. If we consult the Cartesians upon this point, they will tell us, that all we call vegetation or nutrition of plants, is pure mechanism, and that the attraction of the nutritious juice which we attribute to them, is a solemn chimera. If we forsake the Cartesians, and apply to the experimental philosophers, we shall find many of them, who will tell us, that metals and stones grow by means of vegetation; which is an opinion, that not long ago, was illustrated by Joseph Pitton de Tournfort, a celebrated naturalist of the Academy Royal of Sciences at Paris, and more especially, by the celebrated observations he made upon marble in the wonderful cave of Antiparos; and with respect to metals, we, to the authority of others, shall add that of Aristotle, who in his book _de Mirabilibus Auscultationibus_, says, that in a territory of the island of Cyprus, they were used to sow iron, and that it grew and vegetated like other plants.

XLIX. And now we are speaking of Aristotle, we will not omit mentioning an authority of his, which is very applicable to our present subject, because it is totally opposite to a received opinion in the schools, to wit, that plants and animals are of two different genuses, and that the distinction between them is, that the animal is a living sensible entity, and the plant a living insensible one. Aristotle in his book _de Plantis_ says, that oysters and other shell-fish, are both plants and animals: _scimus autem, quod conchyla animalia sunt cognitione carentia: quapropter plantæ sunt, & animalia_. I ask now, how one species can be classed under two diametrically opposite genuses? and how an oyster can be both sensible and insensible? for as an animal, it ought to be a living sensible entity, and as a plant, a living insensible one. Nor can it be said, that Aristotle, when he called an oyster a plant, spoke in a metaphorical sense, for this mode of speaking is not allowed to philosophers, but is only permitted to poets and orators. Besides, the cause he assigns, shews, that he spoke in a rigorous philosophical sense; although, to speak the truth, I do not comprehend who could reveal to Aristotle, that oysters and other shell-fish are destitute of that sort of knowledge, which is proper and natural to the most stupid brutes.

SECT. XII.

L. From the lowest species, we proceed to the next above, and enquire, what is the nature of a living entity; what we are to understand by the term living, and what is life? To this, we shall be answered from the schools, that life is motion _ab intrinsico_, and that living, means that which moves _ab intrinsico_; that is, its motion is produced by some intrinsic faculty, or virtue, which it has within itself.

LI. This definition is incumbered with greater difficulties than the antecedent ones. All the modern philosophers oppose it, although for distinct and contrary reasons. Gassendo, father Maignan, and the other atomists, attribute motion _ab intrinsico_ to atoms, from which dogma it will follow, that motion _ab intrinsico_, is not distinctly peculiar to living animals. The Cartesians are very positive in maintaining, that nothing can give motion to itself, but that all motion in the universe, proceeds from that impulse, which God in the beginning gave to matter, which does, and ever will subsist, without being impaired or injured; and that by virtue of that impulse, motion is communicated from one part of matter to another; so that all which was before at rest, upon its beginning to move, received its impulse from some other body which was in motion before, and transferred its influence to that which was then at rest; and either partly, or in the whole, gave it the power of beginning to move; and they say further, that man, which is the only living corporeal entity they admit, when he moves, cannot be properly said to give motion to his members, but only directs their motion by his will, in virtue of the power antecedently impressed by the impulse of other bodies on the animal spirits.

LII. It cannot be denied, that this doctrine is terribly fortified, by the celebrated maxim of Aristotle, which says, _that every thing that moves, is set in motion by something else_: and although the followers of the common opinion, explain this maxim, so as to render it not incompatible with the definition they give of living entities, there results from this explanation, the inconvenience, that it weakens the principal force of the axiom which they avail themselves of to prove the existence of a first mover, to stimulate a body at rest; for if we suppose, that a living entity has the power of moving itself, we cannot maintain the necessity of a divine influence to produce this motion, without admitting at the same time, the existence of a first mover in other respects, to be established. Thus it seems to me, that the Cartesians can with some colour of reason pretend, that religion is interested in understanding the axiom in all the rigour, which they profess to understand it themselves.

LIII. But be it as it may, with respect to this difficulty, and all others, which the moderns by virtue of their principles can oppose to the doctrine of Aristotle; it is certain, that there may be very serious ones urged against their definition of living entities. Heavy bodies move _ab intrinsico_, and are not living entities. Fire moves _ab intrinsico_, and is not a living entity. The fermentative motion also, according to common physics, is understood to be _ab intrinsico_. And I have remarked and proved in another part of this work, that what the Aristotelites say of heavy bodies being moved by communicated impulse, in the form this explanation is intelligible, is also applicable to the motion of living entities.

SECT. XIII.

LIV. There now only remains within the compass of the predicamental scale, one other thing to consider, which is the highest, and most sublime within the reach of physics, and that is, the nature and composition of the body; but where will this lead us to, the point being equally doubtful with all the rest? The composition of the body, is divided into elemental and mixed; but as this last is composed of the other, unless we know what the elemental is, it is impossible to know of what the mixture consists. Very well; but who knows the nature and number of the elements? To this question, methinks I hear four answers, from four sects of philosophers, which are all different, although each pretends to exclude the others from a competent knowledge of the matter. The Aristotelites say, that they are air, fire, earth, and water. The chymists, that they are salt, sulphur, mercury, earth, and water. The Cartesians insist, that they are composed of the subtil, the globulous, and another matter which is more gross, and which they call the third element; and the atomists, that they consist of the atoms. These are the opinions, which are at present the most prevailing, although there are numbers of others which I shall omit to mention, because they have but few votaries. Now which of these opinions is the true one? Perhaps neither. At least there is but one sect out of the four that admits either of them to be true, and whichever that sect adheres to, the other three assert to be false; which amounts to the same, as saying that one witness deposes to the truth of the matter in question, and that three give testimony against it. Thus no judge to whom the decision is confided, can give sentence in favour of either of the parties; it being out of his power to affirm, that any one of their systems is right and true.

LV. As the audience before whom I propound this reflection, is composed chiefly of the followers of Aristotle, methinks I hear them exclaim, that if we were to collect the suffrages of the academic professors, we should find most votes in favour of his opinion. To this, I reply in the first place, that although a plurality of sectaries, gives greater extrinsic probability to an opinion, still it does not afford certainty, nor intrinsic probability; and the question here, is not whether Aristotle’s opinion is the most probable, but whether it is certain. I reply secondly, that it is doubtful, if we were to include the professors who teach physics in all nations, whether we should in reality find a majority of votes in favour of Aristotle; and unless we could prove by some authentic instrument, that God has limited the knowledge of philosophy to our nation only, and has excluded all others from inheriting the science, I do not know upon what pretension we can ground a right, of admitting none but Spaniards to vote in the question. Some of our antient professors say, that we should not regard the opinions of strangers, because they are novelists; but at the same time, strangers reply, that we should take no account of what the Spaniards assert, because they are obstinate and wrong-headed, and that there is no proof, be it ever so clear, that will make them depart from their old opinions; to which they add, that in Spain, they do not follow Aristotle from choice, but from necessity; for that it requires an heroic spirit, to contradict any thing that has been advanced by Aristotle in that kingdom, where whoever dares venture to oppose him, is instantly assailed by tempests of injuries, which fall on his head like violent hail storms. Nor is even an heroic spirit, sufficient to enable a man to support such an opposition, because the duty of obedience, obliges people not to depart from the line of their school; and this is also frequently the case, in other countries; and from hence, some Anti-Aristotelites have insisted, that the plurality of votes in favour of Aristotle should not prevail, because they cannot be supposed to be free.

LVI. But abstracted from the quantum of extrinsic probability, contained in the doctrine of Aristotle respecting the elements; I assert, that upon a strict examination, you will not find more truth contained in his sentiments, than in those of his adversaries. This opinion, I deduce from the position, that his first qualities consist of four, to wit, heat, cold, wet, and dry, from which in exact proportion, he attributes one to be impregnated in the highest degree with each element, and another near to the highest. This proof, goes lame in innumerable particulars. First, the giving to these qualities the title of first, is conferring a mere voluntary dignity on them, and especially, when we know the invincible difficulty, that attends establishing, that all the others result from them. Secondly, it is very doubtful, whether all the four beforementioned, can properly be called qualities; for many Aristotelites, and with great colour of reason, deny humidity and dryness to be such. That which is humid, is not so from any quality it possesses in itself, but because it has imbibed into its pores some foreign liquid substance, and let that be evaporated, and it will remain dry; from which we may conclude, that humidity is a substance, and that dryness consists in the want of that substance. Thirdly, the appropriating these as two of the four elements, is done without any foundation or reason. In the next place, how can they prove that water is cold in the highest degree? If this was true it would kill us; neither can they prove it so, in a more moderate, or secondary degree, for we are taught by experience, it is indifferent to both cold and heat, according to the agent that is applied to it. It is heated by the fire; and remove it from the fire, and it becomes cool again, not because it has any propensity or natural disposition to be cold, but because it is made so, by the cool atmosphere which surrounds it. There are many other very grave objections to be urged against this doctrine of the four qualities; and therefore the foundation upon which it is built, and the reasoning deduced from it to establish the quaternian system of the elements, are both very slight and futil.

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?

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).