Part III, Chapter 19: Of the different Ways of Reasoning ill, which are called Sophisms (second part)
Taking for a cause that which is not a cause.
This sophism is called non causa pro causa. It is very common amongst men, and we fall into it in many ways. One is, through simple ignorance of the true causes of things. It is in this way that philosophers have attributed a thousand effects to the abhorrence of a vacuum, which, in our time, have been proved to demonstration—and by very ingenious experiments—to be caused by the weight of the air alone, as we may see in the excellent treatise of M. Pascal. The same philosophers commonly teach that vessels full of water break when they freeze, because the water contracts, and thus leaves a vacuum which nature cannot endure. It has, however, been discovered, that they break, on the contrary, because water, when frozen, occupies more room than it did before, which also occasions ice to float in water.
We may refer to the same sophism all attempts to prove by causes which are remote, and prove nothing, things either sufficiently clear of themselves, or false, or at least doubtful, as when Aristotle endeavours to prove that the world is perfect by this reason: The world is perfect because it contains bodies; body is perfect because it has three dimensions; three dimensions are perfect, because three are all (quia tria sunt omnia); and three are all because we cannot employ the word all, when there are but one or two things, but only when there are three. We might prove by this reasoning that the smallest atom is as perfect as the world; since it has three dimensions as well as the world. But so far is this from proving that the world is perfect, that, on the contrary, all body as body, is essentially imperfect, and the perfection of the world consists, principally, in its containing creatures which are not bodies.
The same philosopher proves that there are three simple movements, because there are three dimensions. It is difficult to see how the one follows from the other.
He proves also that the heavens are unalterable and incorruptible, because they have a circular motion, and there is nothing contrary to circular motion. But, 1, we do not see what the contrariety of motion has to do with the corruption or alteration of body. 2, We see still less how the circular motion from east to west is not contrary to another circular motion from west to east.
Another cause which makes men fall into this sophism, is the empty vanity which makes us ashamed to acknowledge our ignorance, for thus it happens that we prefer rather to feign imaginary causes of the things for which we are asked to account, than to confess that we do not know the cause, and the way in which we escape this confession of our ignorance is amusing enough. When we see an effect, the cause of which is unknown, we imagine that we have discovered it, when we have joined to that effect a general word of virtue or faculty, which forms, in our mind, no other idea except that effect had some cause, which we knew well before we found that word. There is no one, for example, who does not know that his pulse beats,—that iron, being near a loadstone, unites with it,—that senna purges,—and that the poppy lulls to sleep. Those who make no profession of knowledge, and to whom ignorance is no disgrace, frankly avow that they know these effects, but that they are ignorant of the cause; whereas the learned, who would blush to confess so much, go about the matter in a different way, and pretend that they have discovered the true cause of these effects, which is, that there is in the pulse a pulsific virtue,—in the magnet a magnetic virtue,—in the senna a purgative virtue,—and in the poppy a soporific virtue. Thus is the difficulty very conveniently resolved; and there is not a Chinese who might not, with as much ease, have checked the admiration which clocks excited in that country, when they were introduced from Europe; for he need only have said that he knew perfectly the reason of that which others thought so marvellous, which was nothing else than that machine had an indicating virtue which marked the hours on the dial, and a sonorific virtue, which sounded them forth. He would thus have become as learned in the knowledge of clocks as these philosophers are in the knowledge of the stroke of the pulse, the properties of the magnet, of senna, and of the poppy.
There are, in addition to these, other words which serve to render men learned at little expense, such as sympathy, antipathy, occult qualities. But still, all these terms would not convey any false meaning, if those who used them would content themselves with giving to these words, virtue and faculty, a general notion of cause, whatever it may be, interior or exterior, disposing or active, for it is certain that there is in the loadstone a disposition which leads iron to unite with it, rather than with any other stone, and men may be allowed to call the disposition, be it whatever it may, magnetic virtue. So that they are deceived only when they imagine themselves to be more learned for having discovered that word, or inasmuch as they would persuade us that through that word we comprehend a certain imaginary quality, by which the magnet attracts iron, which neither they nor any one else ever did comprehend.
But there are others who allege as true causes in nature pure chimeras. This is done by the astrologers, who refer everything to the influence of the stars, and who actually, in this way, have discovered that there must be an immoveable heaven beyond that to which they assign motion, because the earth produces different things in different countries (Non omnisfert omnia tellus; India mittit ebur; molles sua tura Sabaei), the cause of which must be referred to the influences of a heaven, which, being immoveable, has always the same aspect towards different parts of the earth.
One of them, however, having undertaken to prove, by physical reasons, the immobility of the earth, took, as one of his principal demonstrations, this mysterious reason, that if the earth turned round the sun, the influences of the stars would be disordered, which would cause great confusion in the world.
It is by these influences that the people are frightened when a comet appears, or when an eclipse happens, as that one in the year 1654, which was to have upset the world, and especially the city of Rome, as it was expressly said in the Chronology of Helvicus, Roma fa1 alls, although there is no reason why either comets or eclipses should have any considerable effect on the earth, or why causes so general as these should act rather at one place than another, and threaten a king or a prince rather than an artizan. There are, moreover, a hundred of them which have not been followed by any remarkable effect; and it, sometimes, wars, mortalities, plagues, or the death of some prince, happen after comets and eclipses, they happen also without comets and without eclipses. Moreover, these effects are so general and so common, that it would be strange if they did not happen every year in some part of the world; so that those who say vaguely that such a comet threatens some great man with death, do not risk very much.
Author’s note: See the " Thoughts on Comets’’ of Bayle.
It is still worse when they assign chimerical influences as the cause of the vicious or virtuous inclinations of men, and even of their particular actions, and of the events of their life, without having any other ground for doing so, except that of a thousand predictions, it happens by chance that some are true. But if we would judge of things by good sense, we must allow that a torch lighted in the chamber at the hour of birth, ought to have more influence on the body of the child than the planet Saturn, in any aspect, or in any conjunction whatever.
Finally, there are some who assign chimerical causes for chimerical effects, as those who maintain that nature abhors a vacuum, and that she exerts herself to avoid it (which is an imaginary effect, for nature abhors nothing, but all the effects which are attributed to that horror depend on the weight of the air alone), are continually advancing reasons for that imaginary horror, which are still more imaginary. Nature abhors a vacuum, says one of them, because she needs the continuity of bodies for the transmission of influences, and for the propagation of qualities. It is a strange kind of science this, which proves that which is not, by means of that which is not.
Hence, when we engage in seeking after the causes of alleged extraordinary effects, it is necessary to examine with care if the effects are true, for often men weary themselves uselessly, in seeking after the reasons of things which do not exist, and there are an infinite number which ought to be resolved in the same way as Plutarch resolved that question which he proposed to himself, Why those colts which had been chased by the wolves are swifter than others; for after having said that, perhaps it was because those that were slower had been seized by the wolves, and that thus those which escaped were the swiftest; or again, that fear having given them an extraordinary swiftness, they still retained the habit; he finally suggests another solution, which is apparently the real one,—perhaps, says he, after all, it is not true. In this way must be explained the great number of effects which are attributed to the moon, as that bones are full of marrow when it is at the full, and empty when it is on the wane; that the same is true of crawfish, for there are some who say that all this is false, as some careful observers have assured us they have proved, that bones and crawfish are found indifferently, sometimes full and sometimes empty, during all the changes of the moon. The same is true, to all appearance, in relation to a number of observations which are made for the cutting of wood, for reaping and sowing corn, for grafting trees, for taking medicines. The world will be delivered, by degrees, from all this bondage, which has no other foundation than suppositions of which no one has ever seriously proved the truth. Hence the injustice of those who pretend that, if they allege an experiment as a fact derived from some ancient author, we ought to receive it without examination.
We may bring under this kind of sophism too, that common fallacy of the human mind, post hoc, ergo propter hoc. This happens after such a thing, therefore it must be caused by that thing. In this way it has been concluded that the star which is called the dog-star, is the cause of the extraordinary heat we feel during the days which are termed the dog-days, which led Virgil to say, when speaking of that star, which is called, in Latin, Sirius —
Aut Sirius ardor:
Ille sitim morbosque ferens mortalibus aegris Nascitur, et laevo contristat lumine caelum.
Although, as Gassendi has very well remarked, there is nothing more unreasonable than this imagination, for that star being on the other side of the line, its influence ought to be much more powerful in these parts, to which it is more perpendicular; notwithstanding which, the days which we call dog-days here are the winter season there; so that, in that country, the inhabitants have much more ground for believing that the dog-star brings them cold, than we have for believing that it is the cause of our heat.
Incomplete Enumeration. There is scarcely any vice of reasoning into which able men fall more easily than that of making imperfect enumerations, and of not sufficiently considering all the ways in which a thing may exist, or take place, which leads them to conclude rashly, either that it does not exist, because it does not exist in a certain way, though it may exist in another, or that it exists in such and such a way, although it may still be in another way, which they have not considered.
We may find examples of these defective reasonings in the proofs by which M. Gassendi establishes the principle of his philosophy, which is that of a vacuum diffused among the parts of matter, called by him vacuum disseminatum. And we refer to these the more willingly, because M. Gassendi having been a celebrated man, stored with a great fund of curious knowledge, the faults even which may be met with in the great number of works which have been published since his death, are not to be despised, but deserve being known; whereas it is very useless to load the memory with those which are found in authors of no reputation.
The first argument which Gassendi employs in order to prove this diffused vacuum, and which he maintains, in one place, should be considered as a demonstration as clear as those of mathematics, is this: —
If there were no vacuum, and the whole were filled with bodies, motion would be impossible, and the universe would be only one vast mass of rigid, inflexible, and immoveable matter, for the universe being completely filled, no body could move without taking the place of some other. Thus if a body, A, move, it must displace another body at least equal to itself, to wit, B; and B, in order to move, must also displace another. Now this can happen only in two ways,—the one, that this displacing of bodies goes on to infinity, which is ridiculous and impossible; the other, that it proceeds in a circle, and thus the last displaced body occupies the place of A.
There is not here, however, so far, any imperfect enumeration; and it is further true, that it is ridiculous to suppose that, in moving a body, the bodies which displace one another would be moved to infinity. All that is maintained is, that the motion goes on in a circle, and that the last body moved occupies the place of the first, which is A, and that thus all will be filled. This M. Gassendi undertakes to refute by the following argument:—The first moved, which is A, cannot move unless the last, which is X, move. Now X cannot move, because, in order to move, it must take the place of A, which is not yet empty; and therefore, X not being able to move, A cannot either; therefore everything remains immoveable. The whole of this reasoning is founded only on this supposition, that the body X, which is immediately before A, can move on only one condition, which is, that the place of A be already empty when it begins to move; so that, before the moment in which it occupies that place, there be another in which it may be said to be empty. But this supposition is false and imperfect, since there is still another way in which it is possible for X to move, which is, that at the same instant in which it occupies the place of A, A quits that place: and in this case there is no inconvenience.—A pushing B, and B pushing C, and so on to X, and X at the same moment occupying the place of A: in this way there will be motion, but no vacuum.
Now that this is possible, that is to say, that a body may occupy the place of another body at the same moment in which that body quits it, is a thing which we are obliged to acknowledge in any hypothesis whatever, if we admit any continuous matter; if, for example, we distinguish in a rod two parts which immediately follow each other, it is clear that when we move it, at the same instant in which the first quits a space, that space is occupied by the second, and that there is no interval in which we can say that space is void of the first, and not filled by the second. This is still more clear in a circle of iron which turns round its centre; for in this case each part occupies at the same instant the space which has been left by that which preceded it, without there being any necessity for imagining a vacuum. Now, if this is possible in a circle of iron, why may it not be so in a circle partly of wood and partly of air? And why may not the body A, which we will suppose to be wood, push and displace the body B, which we will suppose to be air,—the body B displace another,—and that other another, until X, which will take the place of A at the same instant in which A leaves it?
It is clear, therefore, that the defect of M. Gassendi’s reasoning springs from his belief, that it is necessary in order that a body may take the place of another, for that place to be empty previously, and for at least a moment before, and from his not considering that it is sufficient if it be empty at the same moment.
The other proofs which he adduces are derived from different experiments, by which he showed very clearly that air may be compressed, and that we may force fresh air into a space which seemed already full, as we see in air-balls and air-guns.
On these experiments he founds this reasoning:—If the space A, being already full of air, is able to receive a fresh quantity by compression, it must be either that this fresh air which passes into it, does so by penetrating into the space already occupied by the other air, which is impossible,—or that the air contained in A did not fill it entirely, but that there were between the particles of air void spaces, into which the fresh air is received; and this second hypothesis proves, says he, what I maintain, which is, that there are void spaces between the parts of matter, capable of being filled with new bodies. But it is very strange that M. Gassendi could not perceive that he was reasoning in an imperfect enumeration, and that, besides the hypothesis of penetration, which he judges, with reason, to be naturally impossible, and that of diffused voids between the particles of matter which he wishes to establish, there is a third, of which he says nothing, but which, being possible, renders his argument invalid; for we may suppose that between the greater particles of air there may be a matter finer and more subtile, and which, being able to pass through the pores of all bodies, makes the space which appears full of air able still to receive new air; because this subtile matter, being driven by the particles of air which are forced in, gives place to them by escaping through the pores.
And M. Gassendi was the more called upon to reject that hypothesis, since he himself admits this subtile matter which penetrates bodies, and passes through all pores,—since he considers heat and cold to be corpuscules which enter into our pores,—since he says the same thing of light,—and since he confesses even in that celebrated experiment which he made with the quicksilver, which remained suspended at the height of two feet three inches and a half, in a tube much longer than this, thus leaving a space above which appeared to be empty, and which certainly was not filled with any sensible matter,—since he confesses, we say, that it could not with reason be maintained, that space was absolutely void, since light passed into it, which he held to be a body.
Thus, in filling with subtile matter those spaces, which he maintained to be empty, there would have been as much room left for the entrance of new bodies, as though they had actually been empty.