Aristotle was born at Stagyrus, a city in Macedonia. Having lost his father at an early age, he was, though a mere youth, abandoned to himself, and expended his patrimony in dissipation. At first he followed the carreer of arms, hut soon becoming disgusted with this profession, he left it to resume the favorite studies of his early youth - philosophy and medicine.
The teachings of Plato at that time shed a splendid influence over Greece. Young men flocked to Athens, from all parts, to hear him. Aristotle went also, and showed himself one of his most assiduous and constant auditors. His ardor in study was incredible ; he consecrated to it entire days, and a great part of the nights. It is said that he was obliged, for a living, to take a place in the shop an herbalist, and doubtless he gave medical advice, also, according to the habit of the pharmacopolists of those times. Thus, the philosopher of Stagyrus, the future chief of the Peripatecian sect, belongs to the history of Medicine in several respects, namely, by his birth, and early education : for he was the son of a physician, and received from his father the first elements of science ; secondly, by the profession he practiced during many years of his life ; thirdly, by researches in comparative anatomy and physiology ; finally, by his philosophic doctrine, which maintained its empire for so long a time, over every branch of human knowledge.
When Philip, king of Macedonia, whose finesse and political discernment became proverbial, wishing to give a preceptor to his son Alexander, then fourteen years of age, fixed his choice on Aristotle, and wrote to him on that occasion that well known letter, which not less honors the monarch than the philosopher, we all know how well the young prince responded to the hopes of the father, and the lessons -of the master. I shall say nothing here of the invincible hero who overran and conquered Asia ; but I must not be entirely silent in regard to him, as an impassioned amateur of science and letters, who, in the midst of the embarrassments of the vastest government of the world, and unceasing wars, maintained with his preceptor a scientific correspondence, and not only furnished him the necessary funds to form the first known museum in natural history, but also occupied himself in the collection of animals, plants, and every sort of rare objects, which he transmitted to him from the depths of Asia.
Thanks to the munificence of his royal pupil, Aristotle was in a condition to gather an immense collection of the products of nature - a fruitful mine whence his genius drew an incredible mass of observations, that antiquity never surpassed, in many particulars, and which has 10
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been the astonishment of all ages. Certain critics, not being able to explain how a single man was able to treat so great a number of subjects, and shed so much light on the greater part, have suspected Aristotle of having wickedly destroyed the writings of his predecessors, so as to appropriate their discoveries to himself, just as they accused Hippocrates of having set fire to the temple of Cos, with the design of destroying the archives whence he had drawn the materials of his works - pure calumnies, which fall before the slightest examination, and of which all history has made itself the eternal echo. Every one should read, in the introduction to the Hippocratic works of M. Littre, the natural explanation that this learned philologer gives of the loss of a multitude of ancient .rorks, without resorting to hazardous conjectures against the best established reputations. But the founder of the Peripatecian sect, so far from leaving unmentioned the names of the authors who had written before him on the same subjects, quotes them on nearly every page he often gives their opinions, and many of them are indebted entirely to his quotations for the advantage of having escaped entire oblivion.
The earliest philosophers who meditated on the origin of our knowledge, or the manner in which we acquire it, and the degree of certainty which it offers, were greatly shocked at the frequent and gross errors into which we are drawn by the senses, while they were agreeably surprised, and marvelled at the character of infallibility that certain abstract truths presented, and particularly those that belong to mathematics. To give only one example of this contrast, but one which is everywhere known, do not the most remote astronomical observations demonstrate that the sun and the moon have, in reality, dimensions enormously greater than their objective appearance would lead us to suppose ? From this example, and an infinity of similar ones, philosophers drew this general indication, that the senses transmit false, doubtful, or illusory impressions, and that the soul, to attain the possession of truth and certainty, must isolate itself as much as possible from the intervention of the body, and reflect within itself. Hence arose the contemplative philosophy that Pythagoras recommended in secret to his disciples, and which Plato taught publicly, with all the prestige of his imagination and eloquence.
Nevertheless, men who devoted themselves to the study of physical phenomena, physicians, above all others, could not question the necessity of the intervention of the senses, to obtain a faithful image of these phenomena. Daily experience demonstrated to them how vain are the anticipated conceptions of the mind touching the operations of nature. Each day new deceptions came to lead them to mistrust the principles
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established a priori; for these principles conducted them to consequences that the facts frequently contradicted. Thus, we have found in the Hippocratic collection, authors who proclaim the necessity of banishing from medicine all hypothesis, and holding to immediate observation only ; authors who say that there is no fixed principle of treatment; that the cure of diseases is effected sometimes by contraries, sometimes by similars, and sometimes in other ways, without our being able to say in virtue of what principles.(Traité des Lieux dans l'Honime. Traite' de l'Ancienne Medecine) These are, evidently, empirical maxims, but mere isolated ones, simple perceptions, which constitute neither a system nor a method.
It was reserved for the greatest naturalist of antiquity to lay the first philosophic basis of empiricism ; Aristotle, in emitting his famous axiom, " all ideas come from the senses," (nihil est in intellects, quod non prius fuerit in sensu,) introduced into science a new principle, in manifest contradiction to the revered dogmas of Pythagoras and Plato. It is, then, very important to know how the chief of the Peripatecians would justify, from the beginning, the bold principles which became, two- thousand years later, the germ of a scientific revolution. (This principle was not entirely new, since Plato makes allusion to it in the passages we have cited, when he asks himself if it is not the brain that produces all our sensations, "which produce, in their turn, the imagination and memory, whose operations at last develop science." But Plato scarcely deigned to pause and consider the opinion, while Aristotle adopted and developed it)
We read, in the treatise on Analysis, " It appears that all animals have received, from nature, the faculty of sensation and judgment ; but after a sensation has been produced, some preserve the remembrance of it, and others do not. Those who retain no reminiscence of the impressions, have no idea of the things, beyond immediate sensations. Those, on the contrary, whose soul retains some trace of passed sensations, can, at the end of a great number of such, reason from the recollection which they keep of them. In this way, the memory comes from the faculty of feeling. The remembrance of a thing often repeated creates experience, and experience, that is to say, every general notion which becomes fixed in the soul, relative to the common properties of certain things, abstraction made from their differences - this notion, I say, is the principle of science and art."(Aristotelis Opera Omnia quae extant Grace' et Latine'. Authore Guillemo Duval. Lutitise Parisiorum, anno M. DC.XIX. Analyticorum posteriorum, lib. u, cap. xix)
In another work, the philosopher of Stagy rus recalls the distinction that he has just established between animals which have memory, and those which have not ; he adds, that the first are susceptible of education, while the others possess instinct only. Finally, he says that man alone is capable of instruction and reason ; after which he continues in these terms : "To deduce, from a great number of experiments, a universal idea on an entire class of similar objects, this constitutes art.Thus, to possess the knowledge that a remedy has been useful in a certain disease, in the hands of Callias, Socrates, and several others, is experience ; but to know that such a remedy is good for all individuals of the same species, attacked by a given affection, for example, for all men who are tormented with phlegm, bile, or a hot fever, this is what constitutes art.(Opera Omnia, Metaphys., lib. i. cap. i)
Might not we believe, in reading these fragments, that they arc extracted from some chapter of the modern school of sensualists ? How then does it come that Condillac, one of the coryphse of this school, could write the following lines : " Long ago it was said that all our knowledge originated in the senses. Nevertheless, the Peripatecians were so far from knowing this truth, that notwithstanding the minds of several had appreciated, they were unable to develop it ; so that for several ages afterward it was still a discovery to be made. I am ignorant of the motive of Aristotle, when he advanced his doctrine on the origin of human knowledge ; but I do know that he has left no work in which this doctrine is developed, and that, besides, he sought to be in everything the opposite of the opinions of Plato." (Oeuvres completes de Condillac- analytical extract from the Traite des Sensations. Paris, 1798)
The best excuse that can be given for the epigrammatic insinuation of this last phrase of Condillac is, that he had never read, or had completely forgotten the passages of Aristotle that I have quoted above. There are yet other discoveries, claimed by moderns, the germs of which are found in the writings of this prince of ancient philosophers. The philosophic doubt, for example, which forms one of the pillars of the method of Descartes, is clearly indicated by Aristotle, when he says, " Men who desire to learn, must previously know how to doubt ; for science is only the resolution of previous doubts ; but he who docs not know the knot is unable to untie it." (Metaphys., liv. in., chap. i) The doubt that Aristotle has recommended is very different, as is plain, from that which the Pyrrhornian or Zetetique sect professed. The latter regarded doubting as the highest degree of science ; the Peripatecian, on the contrary, saw only in it, the first step toward the light- a simple disposition of the soul to elevate itself to the intelligence and demonstration of the truth.
Having thus established clearly the claims of Aristotle, as the founder of the sensualist or experimental doctrine, it remains to show in -what particular he afterward separated himself from the doctrine, and established a method diametrically opposite to that of modern sensualists. To show this I will recall the second axiom emitted by this philosopher, on the development of ideas. " The first ideas," he says, " that the sensations create in our minds, are general ones." Here, we observe. the ancient school of the sensualists is entirely separated from the modern, and here, also, commences their antagonism. It is, then, essential to examine upon what considerations Aristotle rests, in advancing such a maxim. He involves in the support of this proposition, the case of a man, who, perceiving at a great distance an opaque mass of vague or undetermined forms, conceives, at first, the general idea of some kind of a body. Then, as he approaches this mass, and sees it moving automatically, he conceives the idea of an animal ; then, finally, when he is near enough, he will not only recognize of what species this animal is, but, also, if he gives attention to certain marks, and particular qualities, he will be able to distinguish it from every other individual of the same species ; in this way he obtains his individual ideas. It is thus, according to this philosopher, that the human mind advances from the most general notions, to those that are particular and individual. He also cites the example of a little child, who calls all men papa, and all women mamma ; but as he grows, his ideas become special, and he learns to discern his father and mother from all other persons. (Aristotle, On Analysis, 2e partie, chap, n and xix. Natural Principles, liv. i, chap, i ; and in several other books)
The argument of Aristotle is captious, and may deceive mere than one reader. It will not, then, be out of place, I think, to recall here the manner in which Locke, one of the chiefs of the modern school of sensualists, explains the succession of our ideas, and the progress of our knowledge. " The ideas," says this writer, " which children form of persons with whom they are familiar, are similar to the persons themselves, and are only special ones. The ideas they have of their nurses and mothers, are very well defined in their minds, and, as so many faithful pictures, represent to them only those individuals. The names that they give them, at first, are limited to them ; thus the names of nurse or mamma, which children employ, are connected entirely to these persons. But after they acquire a greater knowledge of things, and observe that there arc several other beings, who, in respect to figure, and other particulars, resemble their fathers, mothers, and other persons that they are accustomed to see, they form an idea which includes, also, these particular beings, and they call them with all others, men. In this way he obtains a general name, and a general idea. In doing so, however, they form nothing new, but separating themselves from the complex idea they had of Peter, of James, Mary, and Elizabeth, and which was particular to each of them, they retain what is common to them all." (Locke's Essay on the Human Understanding, book ni, chap, in, Â§ 7. See also Condillac, Essai sur l'Origine de nos Connaissance, sec. 5)
The last two quotations, one taken from the writings of Aristotle, the other from those of Locke, offer us the curious spectacle of two metaphysicians, who, starting with the same principle, that all ideas are derived from the senses, separated immediately, to follow opposite routes : the one pretending that the first ideas formed in our minds, by the intervention of the senses, are general ones ; the other affirming that they are always individual in their character. But it is easy to see, that Aristotle, in the sample that he gives, confounds obscure, vague, and undetermined ideas with general ideas, which is a grave mistake, and scarcely conceivable on the part of such a logician as he. Thus, when I say, that the whole is greater than any one of its parts, I express a general idea very clearly ; instead of that, if I perceive an object very distant, not being able to distinguish its form, I have only an individual idea, and that vague and confused. This divergence, so slight in appearance, and nearly imperceptible at first sight, nevertheless, misled in a very unfortunate manner, the philosopher of Stagyrus, and plunged him into an inextricable labirynth of sterile subtilties. Let us follow him for a few moments, in this mistaken route, and see where he ends, relative to the physical and medical sciences.
From the moment our philosopher believed he had proved incontestibly, that general ideas are the first that arc formed in the human understanding, he deduced from it the conclusion, that the study of all the sciences must commence in generalities, or axioms, which he named on that account, principles or elements, and then must pass to particular or individual notions - to the phenomena. So, after having assigned to our ideas an origin, entirely different from Plato, he proceeds to advise the same didactic method, the same mode of acquisition that he does. A pplying this erroneous method to the study of physics, Aristotle commences by asking how many principles there a^3 in nature. He exhibits all the opinions emitted before him on this thorny subject, and after having discussed them, one by one, he ends with the following conclusion, which I translate literally : " Every body knows that the principles or elements exist in antagonism, and it is perfectly reasonable ; for principles can not produce each other, nor be produced by any thing ; every thing, on the contrary, proceeds from them. Thus, we have exhibited what forms the essence of first oppositions - on the one hand, they proceed from nothing, being original ; on the other, they do not mutually produce each other, because they are antagonistic. (1)
Immediately after, he proves, by an argumentation of the same force that natural principles are in number, two or three, namely, the opposition of heat and cold, of dryness and moisture, and finally, the base, or the subject on which these two primitive oppositions must exercise their energy, to which he gives, in another place, the name of ether.
Aristotle admits, moreover, four elements, fire, air, earth, and water, which he believes susceptible of mutual transmutation, and whose laws he describes. Above them, in the most elevated zone of the heavens, floats a fifth element, so called, because it moves rapidly, and eternally in a circle. This was the first and most divine of all the elements, the only one which is imponderable, and immutable ; the only one which was original in its character, being the offspring of none, and yet the basis of all."(Aristotle, Traite' du ciel, liv. i, chap, n, in, liv. iv, chap, v; also in Traite de la Generation, et de la Corruption, liv. 11, chap. iv. ; also on Traite des Meteores, liv. i, chap. in)
We have seen that Plato endeavored to explain all the phenomena of nature, by the consideration of final causes only ; but Aristotle, who piqued himself on being more exact, assigned to each phenomenon, four causes, namely, the material, formal, efficient, and final. Thus, the clay which the potter uses to fabricate a vase, is the material cause of that vase ; the model, or mould after which he forms it, the formal cause ; the potter himself the efficient cause ; and lastly, the purpose for which it is destined, the final cause. (Aristotle. Des Principes Naturel, liv. 11, chap, m., et suiv)
If some of my readers find these details on the Peripatecian philosophy a little too technical - if they do not comprehend what utility the remembrance of these subtile and superannuated distinctions can have for medical men of our times, I pray them to consider that the greater part of the writings of the ancient and middle ages are more or less imbued with them ; so that it would be impossible to read those writings, and particularly the history of medicine, without having at least a superficial notion of the doctrine of Aristotle ; for the medical theory of Galen, which has reigned in the schools down to our own era, is a patent deduction from it. With this short digression, I pass to consider matters which have a connection, more or less direct, with medicine.
Faithful to his method of commencing by principles, Aristotle
(1) Oeuvres d'Aristotle, Des Principes Naturel, liv. i, chap. vi.
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approaches physiology in the most ohscure manner. He inquires, in the first place : What is the nature of the soul - what are its faculties and functions ? To his view, the soul constitutes the essence of all living hodies, vegetable and animal. It is simple, indivisible, and resides in whole in each part of the organized being, as one may assure himself, he says, by dividing a plant, and even certain animals, called insects : for after the division, the separate parts continue to have the same life as the whole structure, which proves that each of them contains the soul integrally.(Traite de Fame, livre i, ch. ix)
The soul is endowed with four primitive faculties, viz : the nutritive, or vegetative, the sensitive, motive, and intellectual. The first three reside equally in all parts of the body, and they are inseparable. The last one - that is to say, the intellectual or contemplative - being of a different species, must have, says our physiologist, a distinct and particular seat. Aristotle does not say positively where its locality is, but we may infer, from various passages in his writings, that he regarded the heart as the special residence of the intelligent soul.(Aristotle. On the Soul)
The vegetative faculty presides over nutrition and reproduction. It is indispensable to all things that are born, live, and die, and is common to plants and animals. The sensitive faculty, on the contrary, exists only in the latter, of whom it constitutes the essence. Vegetables are deprived of it, because they are formed of only homogeneous parts ; that is to say, they originate from one element alone, whilst animals are formed of organic parts, i. e., are composed of various elements. Among animals, there arc some which have the faculty of locomotion ; others are deprived of this ; and lastly, according to him, a very small number of the animal species appear to be endowed with intelligence and reason. (Sprengle. History of Medicine)
This physiologist had no distinct notion of the locomotive apparatus ; moreover, he confounded the tendons and ligaments with the nerves, as we shall show presently, and he designated the muscles by the term flesh.(Du movement des Animaux)
He places the principle of the motive faculty in the centre of the body, for the reason that, in every object that moves, it is necessary that there be a fixed and immovable point which shall serve to sustain all the other parts, and give them impulse. (De la Locomotion. Histoire des Animaux)
See how the desire to give a reason for every thing may lead minds of the keenest perception to offer words void of sense, for veracious and grave explanation ! We have already seen examples of this, and we shall see many more in the course of this history. In place of observing carefully the natural phenomena, and describing them with the greatest possible exactness, man always seems to prefer to carry his judgment beyond sensations; and this is the source of the greatest errors in the domain of physics. Aristotle regards heat and humidity as the two conditions indispensable to life; the duration of which, according to him, is generally proportionate to the volume of the fluids. It is on this account, he adds, that large animals live longer than small ones. That rule, however, is subject to many exceptions, of which the author himself cites examples ; but he is not embarrassed to explain them. (De la longueur et de la brievete de la vie, chap. v. De la jeunesse et de la vieillesse, de la vie et de la mort, chap. iv)
He had no idea of the true functions of the brain, though he describes that viscus much more minutely than any of his predecessors. The following are his remarks : " That which is first found in opening the head, is the brain, and it is placed in the anterior part. All animals possessing a brain, that is to say, all those which have blood, as well as those of the order of molusca, have it generally placed in the same position ; but the brain of man is much more considerable than that of other animals, proportionably to the size of his body, and is also the most humid. The brain is enveloped in two membranes ; that nearest to the cranium is the strongest - the other, which rests immediately upon it, is weaker. The brain is always composed of two lobes, independently of the cerebellum, which lies beneath, and whose form and structure differ from that of the brain. There is usually a little cavity in the middle of the mass of the brain ; its substance is naturally cold to the touch, and neither veins nor blood are ever found in its interior ; but the membrane which envelopes it is full of veins. (Histoire des Animaux, trud. by Camus, Paris, 1783)
There is nothing in all this which refers to the elevated functions of the encephalic organ. Aristotle did not even suspect them ; for he places, as we have just seen, the seat of the soul and of sensation in the heart.
Nor did he know better the functions of the nervous system, what- ever Sprengle, the historian, may say, who attributes to him very gratuitously, in my opinion, the discovery of that apparatus. (Sprengle, Histoire de la Médicine, translated into French by Jourdan. Paris. 1815, T. I, p. 384)
Let every one judge by the following extract : " Let us speak now of the nerves," says the Greek naturalist; "they proceed also from the heart, that viscus containing nerves in its structure - in its largest cavities ; and what is termed the aorta is a nervous vein, whose extremities are nothing else than nerves. At the points where these extremities terminate around the joints of bones, they are not hollow, and are susceptible of the same tension as the actual nerves. But the difference between the nerves and the veins is, that the nerves do not proceed without interruption, from one unique substance to all parts of the body, like the veins. The nerves, on the contrary, are distributed on all sides, and to the articulations of the bones. If they proceeded from the same trunk, their continuity would be apparent in emaciated animals."
" The principal nerves are those of the ham, on which depend the power of leaping ; then another double nerve, called the tendon ; then the extensor and the nerve of the shoulder, which contribute to the strength of the body. No particular name is given to the nerves which belong to the articulations, because all articulations of the bones are bound together by the nerves. In general, the nerves are found in great abundance around the bones, except the bones of the head, which are united by sutures." (Aristotle, History of Animals, livre in, chap. v)
It is evident that in this entire description, Aristotle describes, under the name of nerves, only tendons and ligaments. But Sprengle formed his opinion on the following paragraph : "In the space between the eyes we find three canals which go to the brain ; the largest, the middle one, proceeds to the cerebellum ; and the smallest, the one which is nearest the nose, leads to the brain.” (Sprengle, History of Medicine, t. I, p. 38. Aristotle, History of Animals, livre i, chap. xvi)
He infers from this phrase, that very probably Aristotle had observed the optic and olfactory nerves in fish, where they follow this direction. "Whether or not this naturalist has observed a few nerves, it is nevertheless certain that he did not at all infer their functions.
Aristotle is rich enough in his own merits, without needing to be adorned with the plumes of others. No man in antiquity studied and searched out more things than he, and no one introduced into science so many new facts. To keep to our subject, we assert that, though he never dissected human corpses, he nevertheless corrects many errors on the anatomy and physiology of man, in the Hippocratic collection. For example, he refutes the opinion of Polybius, who supposed that the veins commence at the occiput, from which they descend in pairs the 'length of the anterior, lateral, and posterior surfaces of the body; he asserts that they originate at the head. He combated also the opinion that a part of the fluids drank went directly to the lungs, for the pur. pose of cooling them.(History of Animals)
As he had dissected a considerable number of animals of every species, he compares, with a sagacity astonishing for his era, the organic apparatus by means of which each of them lives, propagates, and fulfills the various functions to which it is destined. In speaking of the heart, for instance, he signalized the varieties of form and structure that this organ presents amongst quadrupeds, birds, reptiles, fishes, etc. He does the same in regard to the digestive tube, the lungs, and the other organs successively. He does not group together, according to the method of naturalists, all the characters that appertain to the same species of animal, so as to distinguish each of them from all the others ; yet his method is not less philosophic nor less fruitful in interesting ideas ; he presents the history of each apparatus of each organic function successively, and shows the varieties and shades in the whole range of the animal scale. In a word, he created comparative anatomy and physiology ; and the plan that he traced is so appropriate to the subject, that, twenty centuries later, George Cuvier did not choose another.
If the founder of the Peripatecian sect can be reproached for having propagated a taste for scholastic subtilties, it must be acknowledged also, that he has furnished an example of patient and attentive observation of nature. His history of animals is a treasure of curious details on the manners and habits of that class of beings, their modes of fecundation and incubation, and their diseases. His disciples, excited by his example and his counsels, cultivated with a praiseworthy zeal, anatomy, physiology and natural history. Theophrastus, his successor, was the most eminent botanist of antiquity. Their reputation in that class of studies, was so well established, that an ancient satirist makes Mercury say, in showing a Peripatecian, whom he wishes to sell, " behold a man who can tell you, in a moment, the duration of the life of a fly ; to what depth the rays of the sun penetrate the sea ; and what is the nature of the soul of an oyster ; he will recount to you, a quantity of other things, more difficult still, on the semen, generation, and the manner in which the fetus is formed in the womb of the mother. "(Luciani Opera - towards the end of the dialogue entitled, Vitarum Anctio ; p. 108, edition of Bourdelat. Paris, 1605)
Plato and Aristotle were among the ancients, the most eminent propagators of two antagonistic opinions, that have divided philosophers, from the origin of science. One of these opinions supposes all our knowledge to be derived from mental intuition, without the intervention of the senses; the other claims that all our ideas are due to sensations. We shall see these two scientific methods, so to speak, parallelly increase, and become more perfect, without either obtaining any decided preeminence over its rival. Both count amongst moderns, partisans of the highest intelligence. It will suffice to name Descartes, Leibnitz, and Kant, for the spiritual school, and Bacon, Locke, Hume, and Condillac, for the sensualist school. We shall, in the course of this history, make it our duty to study, and compare, seriously, the opinions and methods professed by both of these schools, being well convinced that it would be neither just nor reasonable, to agree, exclusively, with the dogmas of either, before diligently examining the teachings of both ; and if my confreres in medicine accuse me of separating myself from my subject, by according too much space to the examination of medical philosophic methods, I reply in this aphorism of the most learned interpreter of the doctrine of Cuvier : " the first question in all science, is always a question of method."