An Introduction to the Study of Experimental Medicine

When an hypothesis is submitted to the experimental method, it becomes a theory, while if it is submitted to logic alone, it becomes a system. A system, then, is an hypothesis with which we have connected the facts logically with the help of reason, but without experimental, critical verification. A theory is a verified hypothesis, after it has been submitted to the control of reason and experimental criticism. The soundest theory is one that has been verified by the greatest number of facts. But to remain valid, a theory must be continually altered to keep pace with the progress of science and must be constantly resubmitted to verification and criticism as new facts appear.

If we consider a theory perfect and stop verifying it by daily scientific experience, it becomes a doctrine. A doctrine, then, is a theory which we regard as immutable, which we take as a starting point for later deduction, and which we believe we are no longer obliged to submit to experimental verification. In a word, systems and doctrines in medicine are hypothetical or theoretic ideas transformed into immutable principles. This sort of method belongs essentially to scholasticism and differs radically from the experimental method. These two methods of the mind, indeed, are contradictory. Systems and doctrines proceed by affirmation and purely logical deduction; the experimental method always proceeds by doubt and experimental verification. Systems and doctrines are individual ; they are meant to be immutable and to preserve their personal aspect. The experimental method, on the other hand, is impersonal; it destroys individuality by uniting and sacrificing everyone's particular ideas, and turning them to the advantage of universal truth as established with the help of the experimental criterion. It advances slowly and laboriously and in this respect will always be less pleasing to the mind. Systems, on the contrary, are alluring because they give us a science absolutely regulated by logic

alone; and that frees us from studying and makes medicine easy. Experimental medicine, then, is anti-systematic and anti-doctrinal by nature, or rather it is free and independent in its essence and does not try to attach itself to any kind of medical system. What I have just been saying about medical systems, I can apply to philosophic systems. Experimental medicine (like all experimental sciences, for that matter) does not need to be attached to any philosophic system. A physiologist's role, like every scientific man's, is to seek truth for its own sake, without wishing to use it to control one system of philosophy or another. When a man of science takes a philosophic system as his base in pursuing a scientific investigation, he goes astray in regions that are too far from reality, or else the system gives his mind a sort of false confidence and an inflexibility out of harmony with the freedom and suppleness that experimenters should always maintain in their researches. We must therefore carefully avoid every species of system, because systems are not found in nature, but only in the mind of man. Positivism, like the philosophic systems which it rejects in the name of science, has the fault of being a system. ITow, to find truth, men of science need only stand face to face with nature, and in following experimental medicine, question her with the help of more and more perfect means of investigation. In this case, I think that the best philosophic system consists in not having any.

As an experimenter, then, I avoid philosophic systems; but I cannot for that reason reject the philosophic spirit which, without being anywhere, is everywhere and, without belonging to any system, ought to reign, not only over all science but over all human knowledge. So even while avoiding philosophic systems, I like philosophers and greatly enjoy their converse. Indeed, from the scientific point of view, philosophy embodies the eternal aspiration of human reason toward knowledge of the unknown. Therefore philosophers always live in controversial questions and in lofty regions, the upper boundaries of science. Hence they impart to scientific thought an enlivening and ennobling motion ; they develop and fortify the mind by general intellectual exercise, while ceaselessly bearing it toward the inexhaustible solution of great problems; thus they nourish a kind of thirst for the unknown; the sacred fire of research must therefore never be extinguished in men of science.

Ardent desire for knowledge, in fact, is the one motive attracting and supporting investigators in their efforts; and just this knowledge, really grasped and yet always flying before them, becomes at once their sole torment and sole happiness. Those who do not know the torment of the unknown cannot have the joy of discovery which is certainly the liveliest that the mind of man can ever feel. But by a whim of our nature, the joy of discovery, so sought and hoped for, vanishes as soon as found. It is but a flash whose gleam discovers for us fresh horizons, toward which our insatiate curiosity repairs with still more ardor. Thus, even in science itself, the known loses its attraction, while the unknown is always full of charm. Therefore the minds that rise and become really great are never self-satisfied, but still continue to strive. The feeling, about which I am speaking now, is familiar to men of science and to philosophers. This is the feeling that made Priestley * say that each discovery we make shows us many others that should be made ; this is the feeling which Pascal expressed in somewhat paradoxical form, when he said : "We are in search never of things, but of the search for things.'' Yet truth itself is surely what concerns us and, if we are still in search of it, that is because the part which we have so far found cannot satisfy us. In our investigations, we should else be performing the useless and endless labor pictured in the fable of Sisyphus, ever rolling up the rock which continually falls back to its starting point. This comparison is not scientifically correct : a man of science rises ever, in seeking truth ; and if he never finds it in its wholeness, he discovers nevertheless very significant fragments ; and these fragments of universal truth are precisely what constitute science.

Men of science, then, do not seek for the pleasure of seeking; they seek the truth to possess it, and they possess it already within the limits expressed in the present state of the sciences. But men of science must not halt on the road ; they must climb ever higher and strive toward perfection ; they must always seek, as long as they see anything to be found. Without constant stimulation by the spur of the unknown, without constantly recurring thirst, it might be feared that men of science would become system-ridden in their acquirements and their knowledge. Then science would halt through intellectual inertness, just as minerals, in saturated solution,

* Priestley, Experiments and Observations on Different Kinds of Air, Introduction, p. 15. become chemically inert and crystallize. We must tlierefore prevent our minds from becoming too much absorbed in the known parts of any particular science or dragging themselves along the ground and losing sight of questions still to be solved. By ceaselessly stirring the inexhaustible mass of unsolved questions, philosophy stimulates and maintains this healthful movement in science. For only the indeterminate belongs to philosophy, in the restricted sense in which I am here considering it, while the determinate necessarily falls into the realm of science. I can no more accept a philosophy, then, which tries to assign boundaries to science, than a science which claims to suppress philosophic truths that are at present outside its own domain. True science suppresses nothing, but goes on searching, and is undisturbed in looking straight at things that it does not yet understand. If we denied these facts, we should not suppress them ; we should only be shutting our eyes and believing there was no light ; we should be sharing the delusion of the ostrich which believes it banishes danger by hiding its head in the sand. In my opinion the true scientific spirit is that whose high aspirations fertilize the sciences and draw them on in search of truths which are still beyond them, but which must not be suppressed, because they have been attacked by stronger and more delicate philosophic minds. Has this aspiration of the human spirit any end, — will it find its limit ? That, I cannot know ; but meantime, as I said above, men of science can do no better than to push steadily forward, because they can always go forward.

One of the greatest obstacles to the free and universal movement of human knowledge is the tendency that leads different kinds of knowledge to separate into systems. This is not a consequence of things in themselves, because everything in nature is connected with everything else and nothing should be viewed in the isolation of a system; but the feeble yet dominating tendency of our minds leads us to absorb other kinds of knowledge into our personal systems. A science that halted in a system would remain stationary and would be isolated, because systematization is really a scientific encysting, and every encysted part of an organism ceases to take part in the organism's general life. Systems therefore strive to enslave the human mind, and, in my opinion, their only ascertainable use is to promote conflicts which destroy them, by stirring and stimulating the vitality of science. We must try, indeed, to break the fetters of

philosophic and scientific systems, as we would break the chains of intellectual slavery. Truth, if we can find it, belongs to every system; and to discover it, experimenters need free movement on every side, without feeling themselves stopped by the barriers of any system. Philosophy and science, then, must never be systematic: without trying to dominate one another, they must unite. Their separation could only be harmful to the progress of human knowledge. Striving ever upward, philosophy makes science rise toward the cause or the source of things. It shows science that there are questions beyond it, torturing humanity, which it has not yet solved. Solid union between science and philosophy is useful to both: it lifts the one and confines the other. But if the bonds uniting philosophy to science should break, philosophy, lacking the support or the counterpoise of science would rise out of sight and be lost in the clouds, while science, without guidance and without high aspiration, would sail at random.

But if philosophy, instead of contenting itself with this fraternal union, tried to enter the household of science and dogmatically lord its productions and its methods of manifestation, then their understanding would cease. Claiming to absorb the special discoveries of a science into any philosophic system would, in fact, be a delusion. For making scientific observations, experiments and discoveries, philosophic method and procedure are vague and powerless; the only means available for that are scientific methods and procedures that can be known only by experimenters, men of science or philosophers, practising some definite science. The different kinds of human knowledge are so entangled and so interdependent in their evolution, that we cannot possibly believe that any individual influence can advance them unless the elements of progress are present in the scientific soil itself. While recognizing the superiority of great men, I therefore still think that, even in their special or general influence on science, they are always necessarily more or less a function of their time. It is the same with philosophers : they can only follow the movement of the human mind, and they contribute to its advance, only by opening the path of progress wider. But in that, they are an expression of their time. No philosopher, coming at a moment when science takes a fertile turn, should create a system, then, in harmony with the movement of science, and afterward cry out that all the scientific progress of his day is due to the influence of his

system. In a word, if men of science are useful to philosophers, and philosophers to men of science, men of science remain free, none the less, and masters in their own house ; as for myself, I think that men of science achieve their discoveries, their theories and their science apart from philosophers. If we meet with incredulity with regard to this, we can perhaps easily prove that, as J. de Maistre says, those who make the most discoveries in science know Bacon ^ least, while those who read and ponder him, like Bacon himself, have poor success. For scientific methods and processes are learned, in fact, only in laboratories, where experimenters grapple with the problems of nature; the young must be gTiided thither first of all; men of riper age have as their portion erudition and scientific criticism which can bear fruit only when we have begun our initiation into science in its true sanctuary, the laboratory. Processes of reasoning should endlessly vary for experimenters, according to the different sciences and to the more or less difficult questions to which they apply them. Only scientific men, and indeed scientific men specializing in each science, can take up such questions, because a naturalist's mind is not a physiologist's mind, any more than a chemist's mind is a physicist's. As for Bacon and the other more modem philosophers who try a general systematization of precepts for scientific research, they may seem alluring to people who look at science only from a distance ; but works like theirs are of no use to experienced scientists; and by false simplification of things, they mislead men who wish to devote themselves to cultivating science. What is more, they embarrass them by burdening the mind with vague and inapplicable precepts that we must hasten to forget if we wish to become true experimenters.

I have said that scientific men and experimenters can be educated only in special laboratories of the sciences they wish to cultivate and that precepts are useful only when derived from the details of experimental practice in some definite science. In this Introduction, I have tried to give as exact an idea as possible of physiological science and of experimental medicine. However, I am far fom presuming to believe that I have given rules and precepts which experimenters should follow rigorously and absolutely. I have tried merely to study the nature of the problems to be solved in the experimental science of living beings, so that everyone might thoroughly under- • J. de Maistre. Examen de la philosophie de Bacon, Vol. I, p. 81.

stand the scientific questions belonging to the domain of biology and know the means which that science now has to attack them. I have quoted examples of investigation, but have been very careful not to give needless explanations or to formulate a single or absolute rule; because I think a teacher's role should be limited to clearly showing his pupil the goal that a science sets itself and to pointing out all possible means at his disposal for reaching it. But a teacher should then leave his pupil free to move about in his own way and, according to his ovm nature, to reach his goal, only coming to his aid if he sees that he is going astray. I believe, in a word, that the true scientific method confines the mind without suffocating it, leaves it as far as possible face to face with itself, and guides it, while respecting the creative originality and the spontaneity which are its most precious qualities. Science goes forward only through new ideas and through creative or original power of thought. In education we must, therefore, take care that knowledge which should arm the mind does not overwhelm it by its weight, and that rules, intended to support weak parts of the mind, do not atrophy the strong and fertile parts. I need not enter into further explanations here; I have had to limit myself by forewarning biological science and experimental medicine against exaggerating the importance of erudition and against invasion and domination by systems; because sciences submitting to these would lose their fertility and would abandon the independence and freedom of mind essential to the progress of humanity.

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