can only report the extraordinary unanimity above mentioned, a unanimity which was doubtless at bottom the reason why the Medico-Psychological Association could so readily bring about an adoption of its classification. Whatever anybody's doubts as to the details thereof, the classification could certainly be practically used. I hope only, from the point of view of general developments in mental hygiene, that the committee will be a truly standing and dynamic committee, ready to consider year by year modifications which may be proposed, to the end that possibly at the expiration of either a hemi-decade or a decade, the classification may be revamped.

But how shall any classification of mental diseases be employed? How shall we approach the classifying of mental diseases, as we, for example, approach the classification of an unknown plant or animal? What are the processes employed in actual diagnosis aside from the methods of collecting data and observation? This is no merely academic task. It has been the daily task of the Psychopathic Hospital in Boston during the last six years and in the practical handling of over 10,000 cases, a large minority of which are decidedly doubtful as to their place in any psychiatric nosology. This task must also be very prominent, as indeed the reports of these institutions show, in such hospitals as the Psychopathic Ward at Ann Arbor, the Bellevue Psychopathic Ward, and perhaps to a less extent in the Psychopathic Hospital in Cook County, Illinois. After the youthful aspirant to honors gets over his initial confusion at variations in nomenclature and becomes cognizant of the chief constituents of psychiatric nosology by their actualities if not by their names, how shall he consolidate his progress and generalize his diagnostic method? It is somewhat in psychiatric diagnosis as in the learning of an intellectual game, such, for example, as chess: the early difficulties as to nomenclatural variations correspond to the initial difficulties in learning the names and movements of chess men, but this superficial and early difficulty in chess is speedily replaced with difficulties of an entirely different logical nature.

The chess enthusiast now reads chess books, goes over game variations, studies openings and endings, and tries to become an accomplished chess player through transfer of book knowledge to his practice. In this effort he naturally, as in all other depart

ments of science and art, always fails. He then acquires through practice, with continual reference to books or authorities, that measure of true chess knowledge which he is able to attain. He now becomes equipped with certain chess fundamentals, not too easy to reduce to propositions, although some endeavor has recently been made to accomplish this even in that most complex of all games-chess.

The medical problem of diagnosis in mental disease resembles more closely the process of classification of plants and animals than it does the choice of lines of play in chess. Probably in a later stage of psychiatric science, we shall find, in the choice of therapeutic terms and in their pragmatic modifications, much more of an analogue to the difficulties of chess.

But, it may be asked, how is it possible to reduce the classification of mental diseases to such simplicities as now run in botany or zoology? One could not hope for quite the definiteness which prevails in the taxonomies of biology when one has to deal with any form of disease, let alone the mental diseases. Still, after all, the distinction between genera and species is a distinction which is not at all confined to botany and zoology, but is a most ancient logical distinction, found at least as early as the Greek logicians. Heads and sub-heads have been known to all thinking persons since thinking persons arrived on the scene.

Out of purely practical considerations, there was developed from the Psychopathic Hospital experiences what I termed a "Key to the Practical Grouping of Mental Diseases," published in the Journal of Nervous and Mental Disease for January, 1918, in which mental diseases were divided roughly into II great groups, corresponding somewhat accurately to the so-called botanical or zoological "orders." Above I mentioned the fact that some persons do not readily distinguish between nomenclature and classification and consider that, where there are many nomenclatural divergences, there are also many divergences in classification. I said that facts proved, on analysis of leading American psychiatric text-books, that despite sundry differences in nomenclature, their classifications betrayed an extraordinarily single mind on the part of American psychiatrists. Now I find that other persons, who shall also be nameless, find it difficult to distinguish not only between nomenclature and classification, but

between classification and a key to a classification or the method by which a classification is used.

Conceding that the American Medico-Psychological Association's classification, adopted as it has been by a great number of American institutions and by the United States Government for war purposes, is a reasonably good classification and aware that its constituent elements fairly well correspond with what all American psychiatrists fundamentally agree upon, the problem still remains, how shall this classification be used; how shall we arrive at the result that a given case falls into one of the 22 groups listed by the Association's committee?

Again I find that, just as some persons fail to distinguish nomenclature and classification and others fail to distinguish classification and key, so still others fail to distinguish between the process of diagnosis and the process of collecting facts upon which a diagnosis is grounded. I find no special divergences of opinion on the part of American psychiatrists as to the methods of observation; that is, the art of collecting data of observation. To be sure, there is one eminent neurologist who triumphantly proclaims that he knows really no one or hardly any one who can take a knee-jerk; but this kind of claim of superiority in the art of observation is hardly to be endured save by some process of cleverly adapted ridicule. There is really no important split in the psychiatric world upon the methods of collecting data. Even the perennially diurnal methods of collecting a clinical history, recommended by the Freudians, do not logically differ from the scandalously inadequate cheese-boring methods adopted by the unregenerate psychiatrist of every-day life.

Suppose then that,

A, nomenclatural divergences be for the moment forgotten; suppose that,

B, some classification, e. g., the A. M.-P. A.'s classification, be accepted as containing all the constituents wanted for statistical tables; and suppose that,

C, the collectors of data are duly making proper observations according to modern standards, there will still remain the question of the process of logically arriving at a diagnosis; that is, a diagnosis of the entity to which the case may be supposed to belong.

I find, however, that there are some persons who choose to deny that there are any psychotic entities and presumably that there are any pathological entities whatever. The term entity for these persons appears to have some bristling dread arcanum about it, having a smack of metaphysics; inasmuch as every individual is, through the fact of his being an individual, so very different from every other individual, how can we compress him into an entity? Shall we not do him therapeutically an enormous injustice by subsuming him under any head whatever? Here, in my opinion, is an extraordinary overdevelopment in application of the principle of identity of indiscernibles. Was it not Leibnitz who proved or proclaimed that no two leaves of grass were identical with one another? By the same token, should we not all agree that no two persons and, à fortiori, no two psychopaths are at all alike? And does not this assertion mean that we cannot put any two psychopaths into one entity? This is not the place in which to discuss the inner spirit of the principle of the identity of indiscernibles; but I confess that those persons who overemphasize the principle of individualization are to my mind just as little at ease in the logical world as those who are forever generalizing. Without further argument, therefore, I want to say that I have no objection to any entity whatever, provided there is a good argument in the general psychiatric mind for its existence.

The argument in my brief paper entitled "A Key to the Practical Grouping of Mental Diseases" was an argument for an application of the original principle of order, a principle which has been greatly developed in modern logic. I have put a few historical remarks upon this matter in a paper to be shortly published in the Journal of Clinical and Laboratory Medicine, entitled "Diagnosis per Exclusionem in Ordine: General and Psychiatric Remarks." In this paper I have called attention to the late Professor Royce's remarks upon the principle of order in modern logic and have given some reasons why it seems to me an important thing for medical diagnosis to follow this modern line of logical developments. It will be wise, however, to emphasize in this inductive age that the considerations in the paper called "A Key to the Practical Grouping of Mental Diseases" were born in practice and not in books of logic. The fact is, that in mental diseases there are few or no reliable indicator symptoms.

I have tried to develop this point somewhat more in detail in a paper "On the Genera in Certain Great Groups or Orders of Mental Diseases" presented before the Neurological Association and to be shortly published. The fact that there are practically no indicator symptoms of particular mental diseases led me to be able to say to the neurologists the following: "Let a young diagnostician of the dogmatic or slightly paranoid type get the initial idea that a case belongs in the dementia præcox group, he will be able to defend his thesis against all comers by the use of symptom lists founded upon the very best text-books. In fact, the better the text-book, the easier for the young tyro to carry his point for the time being."

In short, if we attempted to use in the field of psychiatric diagnosis any such scheme as that of the "presenting symptoms" of Richard Cabot's formulation, we should land in quagmires of classification. For any presenting symptom, e. g., mania, depression, grandiosity, delusion, even hallucination, would suggest any one of a great quantity of mental diseases. Some small tip or "hunch" would then suggest that the said symptom belonged in group X. Upon reference to books of authorities, said symptom would be unfailingly found in group X. A great number of collateral symptoms would also be found therein. To be sure, the systematist might have given some little idea of the statistical frequency of the given symptom; but he would be careful to say, for example, that a depression is occasionally found in dementia præcox and that auditory hallucinations are occasionally found in manic-depressive psychoses. The tyro bent upon making a diagnosis of one or other of these diseases would hardly get the statistical nuances of the entire situation.

Without going into this matter of the lack of indicator symptoms in the field of mental diseases, I think it will be conceded by all that a young diagnostician (or even an academic old one) is very often able to press the phenomena of practically any case into any one of half a dozen groups. Hence the obscurity and the delights of psychiatric diagnosis !

Where there are no indicator symptoms, it seems desirable to examine the entire logical material in an orderly way, confronting in sequence the various possibilities. This might be done by lot or in some other arbitrary fashion, as, for example, by an