None the less it will be long before official science ceases to regard the study of physiognomy as illegitimate. Although people will still believe in the parallelism of mind and body, they will continue to treat the physiognomist as as much of a charlatan as until quite recently the hypnotist was thought to be. None the less, all mankind at least unconsciously, and intelligent persons consciously, will continue to be physiognomists, people will continue to judge character from the nose, although they will not admit the existence of a science of physiognomy, and the portraits of celebrated men and of murderers will continue to interest every one.
I am inclined to believe that the assumption of a universally acquired correspondence between mind and body may be a hitherto neglected fundamental function of our mind. It is certainly the case that every one believes in physiognomy and actually practises it. The principle of the existence of a definite relation between mind and body must be accepted as an illuminating axiom for psychological research, and it will be for religion and metaphysics to work out the details of a relationship which must be accepted as existing.
Whether or no the science of character can be linked with morphology, it will be valuable not only to these sciences but to physiognomy if we can penetrate a little deeper into the confusion that now reigns in order to find if wrong methods have not been responsible for it. I hope that the attempt I am about to make will lead some little way into the labyrinth, and will prove to be of general application.
Some men are fond of dogs and detest cats; others are devoted to cats and dislike dogs. Inquiring minds have delighted to ask in such cases, Why are cats attractive to one person, dogs to another? Why?
I do not think that this is the most fruitful way of stating the problem. I believe it to be more important to ask in what other respects lovers of dogs and of cats differ from one another. The habit, where one difference has been detected, of seeking for the associated differences, will prove extremely useful not only to pure morphology and to the science of character, but ultimately to physiognomy, the meeting-point of the two sciences. Aristotle pointed out long ago that many characteristics of animals do not vary independently of each other. Later on Cuvier, in particular, but also Geoffrey St. Hilaire and Darwin made a special study of these “correlations.” Occasionally the association of the characters is easy to understand on obvious utilitarian principles; where for instance the alimentary canal is adapted to the digestion of flesh, the jaws and body must be adapted for the capture of the prey. But association such as that between ruminant stomachs and the presence of cloven hoofs and of horns in the male, or of immunity to certain poisons with particular colouring of the hair, or among domestic pigeons of short bills with small feet, of long bills with large feet, or in cats of deafness with white fur and blue eyes—such are extremely difficult to refer to a single purpose.
I do not in the least mean to assert that science must be content with no more than the mere discovery of correlations. Such a position would be little better than that of a person who was satisfied by finding out that the placing of a penny in the slot of a particular automatic machine always was followed by the release of a box of matches. It would be making resignation the leading principle of metaphysics. We shall get a good deal further by such correlations, as, for instance, that of long hair and normal ovaries; but these are within the sphere of physiology, not of morphology. Probably the goal of an ideal morphology could be reached best not by deductions from an attempted synthesis of observations on all the animals that creep on the land or swim in the sea (in the fashion of collectors of postage stamps), but by a complete study of a few organisms. Cuvier by a kind of guess-work used to reconstruct an entire animal from a single bone: full knowledge would enable us to do this in a complete, definite, qualitative and quantitative fashion. When such a knowledge has been attained, each single character will at once define and limit for us the possibilities of the other characters. Such a true and logical extension of the principle of correlation in morphology is really an application of the theory of functions to the living world. It would not exclude the study of causation, but limit it to its proper sphere. No doubt the “causes” of the correlations of organisms must be sought for in the idioplasm.
The possibility of applying the principle of correlated variation to psychology depends on differential psychology, the study of psychological variation. I believe, moreover, that a combination of study of the anatomical “habit,” and the mental characteristics will lead to a statical psycho-physics, a true science of physiognomy. The rule of investigation in all the three sciences will have to be that the question is posed as follows; given that two organisms are known to differ in one respect, in what other respects are they different? This will be the golden rule of discovery, and, following it, we shall no longer lose ourselves hopelessly in the dark maze that surrounds the answer to the question “Why?” As soon as we are informed as to one difference, we must diligently seek out the others, and the mere putting of the question in this form will directly bring about many discoveries.
The conscious pursuit of this rule of investigation will be particularly valuable in dealing with problems of the mind. Mental actions are not co-existent in the sense of physical characters, and it has been only by accidental and fortunate chances, when the phenomena have presented themselves in rapid succession in an individual, that discoveries of correlation in mental phenomena have been noticed. The correlated mental phenomena may be very different in kind, and it is only when we know what we are after and deliberately seek for them that we shall be able to transcend the special difficulties of the kind of material we are investigating, and so secure for psychology what is comparatively simple in anatomy.