AN ESSAY ON THE PHILOSOPHY OF MEDICAL SCIENCE. By THE disposition to eschew hypothesis as a guide for medical practice, and to fall back upon diligent observation, is rapidly augmenting in this country; and we should feel at a loss at the present time to point to any dominant theory assuming the empire over the mind of observers similar to that once possessed by the systems of Darwin, Cullen, or Brown. This is a matter for congratulation; for although almost any system may furnish some useful practical indications, yet the evil it produces by its exclusiveness, and by diverting attention from the true path of inquiry, infinitely preponderates over any resulting benefit. The object of the present Essay is to demonstrate that all Science, properly so called, must have its foundation laid, and in fact consists in, the careful observation of facts, and not in à priori or hypothetical reasoning. It is still more important that fanciful hypothesis should not be our guide in medical science than it is in physical science, inasmuch as the practical results of erroneous views are of so much more vital consequence. In the first part of his work, Dr. Bartlett sets forth the characters of true physical science; and in the second, exhibits the precisely similar nature of medical science, as well as some of the obstacles which oppose themselves to its completeness, and to its pursuit. In each of these there is matter that will prove interesting to our readers. PART I. THE PHILOSOPHY OF PHYSICAL SCIENCE. The purport of the entire work may be said to be briefly stated in the first proposition advanced by the author, that "all physical science consists in ascertained facts, or phenomena, or events; with their relations to other facts, or phenomena, or events; the whole classified and arranged." The following observations upon the partial apprehension of this statement, even by those who profess to reject all à priori reasoning, are deserving of attention. "I believe, nevertheless, it is true, that there has always been, and that there still is, in the minds of most men, and in those of philosophical thinkers, a somewhat imperfect, or confused, apprehension of its doctrines. I do not think that its truth is seen and felt, as it should be, in the simplicity, the purity, and the absoluteness, which belong to it. The confusion to which I allude, is this. There seems to be a common feeling, that the facts, phenomena, and events, with their relationships, classified and arranged, constitute, not the entire science, to which they belong, but only the foundation of the science. There is a feeling that these facts and relations are to be used as elements, out of which the science is to be built up, or constructed, by what is called inductive reasoning. The feeling implies, and the avowed doctrine growing out of it, often asserts, that the science is in this subsequent process of reasoning, and not in the facts, themselves, and their relationships. We are constantly told that the facts are to be used as materials, to be sure; that it is not safe to take for our materials any thing but facts; that they constitute the basis of every science; but, after all this, the No. 100. 23 essential condition and constitution of the science is often placed, more in the process of reasoning, as it is called, than in the facts and their relationships. Now what I wish to insist upon is this: that the science is in the facts and their relationships, classified and arranged, and in nothing else. The science, thus constituted, is, so far, complete; no proof of inductive reasoning, or of any other reasoning, no act of the mind can add any thing to what has already been done. * Words are things; and I cannot doubt, that much obscurity and confusion would be removed from our conceptions of the nature of the philosophy of science, if this long-abused term, inductive reasoning, could be suffered to disappear from the language of science and philosophy; and if, for the indefinite and shadowy ideas, which it so often expresses, or attempts to express, could be substituted those, which are so clearly and obviously contained in the phraseology,—the classification and arrangement of phenomena and their relationships." * # * * * As illustrative of this view of the nature of the philosophy of physical science, Dr. Bartlett cites the phenomena of gravitation, which, observed and classified, form the science completely, and exclusively of any subsequent process of reasoning. That a knowledge of these various facts or phenomena, with their relationships, can only be acquired by observation, or experience, is admitted in a general way frequently, without a full appreciation of the consequences of such admission. The necessity of each class of phenomena or relationships being separately submitted to this process is not sufficiently allowed, and the possibility of deducing the existence of certain of them from the knowledge of the existence of certain others, is too readily admitted. After giving various illustrations of the independence of these classes of phenomena of each other, as regards the proof of their exist. ence, the author observes :— "There is another seeming qualification of the doctrine, that I am endeavouring to illustrate, about which it may be requisite to say a few words. It has often been alleged, for instance, that Sir I. Newton inferred, by a process of à priori reasoning, the combustibility of the diamond, before such combustibility had been demonstrated by observation. But what did Newton really do in this case? Manifestly this, and nothing more. A relationship had already been noticed between two certain properties or phenomena.-at least in many bodies; to wit, their refractive power and their combustibility. Newton's reasoning, as it is called, consisted, simply, in the suggestion, or conjecture, that this relationship might be absolute and universal; and, if so, that the diamond would prove to be combustible. The only reasoning in the case consisted in the application to new circumstances of an assumed relationship. It has been said of Fresnel, that he proved by a most profound mathematical inquiry, à priori,' the existence of certain subtle properties of polarized light. But here, again, what did Fresnel really do? He showed, by the agency of his mathematical calculations, that certain relationships of light, assumed or ascertained by observation, in certain conditions, must, if these relationships were true and genuine, exist, also, in all other identical conditions. He showed that, if certain modifications of light, wrought in its properties, by the action of Iceland spar, during its passage through this substance, were dependent upon certain peculiarities in its crystalline structure, then the same modification must be produced in other substances, identical in these peculiarities of structure with the Iceland spar. He applied, merely, and generalized, by means of his calculations, a phenomenon, or relationship of light, already ascertained by direct observation." 25. A law or principle of physical science is defined as consisting "in a rigorous and absolute generalization of the facts, phenomena, events, and relationships, by the sum of which, science is constituted; and in nothing else. It is identical with the universitality of a phenomenon, or the invariableness of a relationship." It is this universitality and unchangeableness of the tendency of all substances, left at liberty, to approach each other, that constitutes the law of gravitation. So, too, with the refrangibility of the rays of light, and various other well-ascertained phenomena. The Nature and Value of Hypothesis.-The author defines hypothesis as "an attempted explanation, or interpretation of the ascertained phenomena and relationships, constituting science: and it is nothing else. It consists in an assumption, or a supposition, of certain other unascertained and unknown phenomena. It does not constitute an essential element of science. All science is absolutely independent of hypothesis." The desire of explaining the nature of the various phenomena which are only partially known and appreciable by us, has possessed the inquiring spirit of man in all times but its exercise must not be confounded with and considered as part and parcel of science. The various speculations upon the ultimate constitution of matter, even such as have all the plausibilities and probabilities in their favour, as that of the Atomic Theory, are at best but conjectural, having numerous incongruities to contend with, and liable to be dissipated as the field of knowledge enlarges and yet the facts to be explained, and the co-ordination of phenomena remain immutable. Thus, the facts and science of optics remain unchanged, although the Newtonian hypothesis respecting their nature is abandoned by nearly all enquirers. A supposed use of hypothesis is thus commented upon :— "There is one very common feeling in regard to these interpretations and explanations, which is, that they render the phenomena, to which they are applied, more intelligible-more easily comprehended and understood than they otherwise would be. It seems to me, that there is some fallacy in this feeling, or at least, that its alleged value is exaggerated. We shall find, I think, on a close examination of the matter, that the difficulty to which I refer, is only changed in the place which it occupies, by these explanations; that it is neither removed, nor very materially diminished by them." This opinion is illustrated by inquiring as to what extent is the comprehension of the phenomena of gravitation really rendered more easy by Newton's assumption of the intervention of an invisible æther. The explanation is nowise facilitated by the supposed addition of this material but invisible substance, one difficulty only being substituted for another. The same observation applies to the various theories of light, electricity, chemical attraction, &c. Dr. Bartlett, however, by no means denies that hypotheses, properly employed, may have their great uses. "Without qualifying, in any degree, the doctrine I have been endeavoring to elucidate, that all science is independent of hypothesis, I am quite willing to admit, that hypothesis has often been of service to science, in suggesting, guiding, and directing its researches. I am willing to go farther than this, as has already been intimated, and to admit, at least the possibility, in some instances, that the researches thus suggested and directed, may lead ultimately to the positive demonstration of the assumed phenomena, constituting the theory. I am willing to admit with Professor Whewell (the speculative tendencies of whose mind are very evident in all his writings) the great difficulty, perhaps the impossibility, in many cases, of forming any definite conception of phenomena, or reasoning upon them, without resorting to some hypothetical machinery, for the purpose of expressing their nature and relations. But after all, I cannot avoid repeating the conviction, that an undue importance, and a false position. is still very generally assigned to these interpretations. The old and illegitimate usurpation of power by the IDEAL PHILOSOPHY, in the empire of science, is even yet only partially destroyed; and the reign of EXPERIENCE, with that divine right, and absolute dominion, which constitute her inalienable prerogatives, has been only partially established. It is important to observe, farther, that the aids and uses, which may really be derived from hypotheses, will in no way be diminished, but increased rather, by assigning to them the subordinate character and station, which they ought always to occupy. If this is done, while their ability to advance the progress of science will not be in any degree lessened, their mischievous tendencies in obscuring its perceptions, and in leading it astray, will be neutralized." 48. As a makeweight against the authority of Sir John Herschell and Mr. Whewell, the two great advocates for an extended use of hypothesis, the author cites the opinions of Newton and Davy deprecating their undue influence. Dr. Bartlett furnishes the following definition of a theory: "Theory is one of two things, according to the manner in which the word has been used. It is either a generalization of phenomena, and relationships, and in this case, identical with a law, or principle, of science; or it is an attempted explanation of phenomena, and relationships, through the intervention of other assumed and unascertained phenomena, and relationships, and, in this case, identical with hypothesis." Classification of phenomena and their relationships is essential to the constitution of science. Certain groups, possessing identity or similarity, require to be arranged together, in marked contradistinction to others, evincing dissimilarities, and in proportion as this is accomplished is the classification a natural one. All is confusion until this is effected; for the mere heterogeneous accumulation of facts may be an unavoidable preliminary, but it is their due arrangement and classification alone that can be said to constitute science. PART II. THE PHILOSOPHY OF MEDICAL SCIENCE. If the temptation to pass from the true path of inquiry and deduction proves often too great for the cultivators of physical science, where so much is known, and so many relationships incontrovertibly established; we may believe that, in the investigation of the science of life, in which the facts acquired are so much fewer in number, and their relations to each other far less obvious, the resort to à priori reasoning and hypothesis will be of still more frequent occurrence. "The feeling has been much more common in medical, than in physical science, that although facts and their relations might, indeed, and must constitute the foundation of the science, the science still consisted in something more than these facts and relations;—that, upon these latter the science itself was to be somehow built up by that magical and creative process of the mind,-that evil genius of medical science, called, indeed, induction, but differing, when stripped of its disguises, in no single function or attribute, from that speculation, the place of which it professed, with promises as loud and pompous as they have proved to be barren and empty, to occupy. The feeling has been, and still is, as much, almost, since the time of Bacon as before,-that the science is in the inductive or reasoning process, superadded to the facts and their relations, more than in these latter themselves. Here, at the commencement of this part of my essay, I wish to enter my protest against this doctrine, in all its forms and modifications. I wish to show, that the science of medicine consists in the phenomena of life with their relationships classified and arranged,-WHOLLY, enTIRELY, ABSOLUTELY. I wish to show that these elements constitute, not the foundation upon which, nor the materials merely with which, the science is to be subsequently constructed, by some recondite and logical process of the reason, -but that they are the science, and the whole science, already constructed, and so far completed: and that nothing can be superadded to them, by any act of the mind, which can in any way increase their value, or change their character." 69. So important do we regard the inculcation of the necessity of the study of facts as the only legitimate foundation of all science, that we have perhaps allowed the author to repeat himself too often in the extracts we have made from his book. We may, however, now state, that we believe he has in some measure raised a phantom for the mere purpose of destroying it, and that a portion of his objections at least are resolvable into a misapprehension of terms. Far be it from us to state that the so-called medical science even of our own day is not disfigured by hasty conclusions and crude hypotheses. That it is so, and must continue to be, until a more laborious system of observation is recognized as essential (which it is however more and more every year) does not admit of doubt: but we are quite at a loss to know how progress is to be effected if the new facts acquired are not to be submitted to the process of induction. In what other manner are our principles for the comprehension and treatment of disease to be acquired? In fact, the author, in one proposition of his essay, contradicts the conclusions of another: for, while he repudiates all idea of science being dependent upon induction, he at the same time asserts that the acquisition of facts and phenomena is useless, unless they be submitted to due classification and arrangement. Truly it is so; but this very classification of a large body of facts is but another terin for a generalization of them, which generalization is in point of fact the induc tive process itself; and no scientific law or principle can possibly be laid down until it has been gone through. The author has had in view the numberless instances of induction from an insufficient number of facts, and the dangerous consequences of reasoning from false analogies: but such perversions as these no-wise justify his indiscriminate and inconsistent condemnation of the process of induction, when legitimately carried out. We recommend to the notice of our readers the most able statement upon this subject we are acquainted with, namely, a Lecture delivered some years since by Dr. Ferguson, upon "The Method of Induction and its Results on Medical Science. * Appendix to his Treatise on Puerperal Fever, 1839. 1 |