The postulate of the "Positive" School, with which the name of the celebrated Professor Lombroso will always be associated, is that crime or criminality is a morbid or pathological state akin to disease, or, in other words, an abnormal state, due to certain physical or mental defects, made manifest by certain stigmata or "tares physiologiques"—the result either of inherited defect or reversion to atavistic type, or in short, that there is "a criminal type" i.e., a race of beings predestined to criminal acts, against whom any system of punishment would be futile, as by nature such beings would not be amenable to the deterrent influences of penal law. This theory—of which the logical result would be either elimination of the unfit, or the translation into the province of medicine of all legal procedure—has failed to command general assent or approval. Like all half-truths, it is extremely dangerous, for it is, of course, the fact that morbid conditions are associated, to a certain degree, with crime, and, like all sensational dogmas, based on untested observation, it affected the public imagination, prone to believe that the criminal is a sort of "bogey-man"—the stealthy enemy of peaceful persons, ever ready to leap in the dark. This uneasy feeling encouraged the idea that the criminal was a class by himself—an abnormal being, the child of darkness, without pity and without shame, and with the predatory instincts of a wild beast. Thus gradually the common belief has taken root that there is a criminal type, and that it is persons of this particular brand or species who commit crime, and go to Prison. This belief is what Dr. Goring calls the great "superstition" of the day, which stands in the way of Prison reform, which darkens counsel in dealing with crime, which renders rehabilitation difficult, and which stifles and discourages the zeal of the philanthropist, to whom the "criminal" is a man of like passions with himself, and amenable to the same influences; and not predestined to crime and anti-social conduct, from which no human effort could save him.

The peculiarity of the Lombrosian doctrine was in the attempt made by it to "stamp a preconceived idea with the hall-mark of science; to support an à priori conception of 'abnormality' by an alleged scientific method of investigation;" but the methods of Lombroso were scientific only in name. He sought to solve those infinite and delicate relations which exist in all human or social conditions by observation alone. He brought much acumen, a great diligence, and imagination to the examination of the subject, but his field of observation was limited. If criminality were a morbid state, with signs comparable to those of disease, observation alone would suffice; but, in fact, there are no characteristics, physical or mental, peculiar to criminals, which are not shared by all people. It is common to speak of poverty, drink, neglect, &c., as the "causes" of crime; but such a causation can only be established by the statistical method of averaging large numbers, with the view of proving that the tendency to anti-social conduct is, in fact, associated with the personal, economic, and social condition of an individual. "The science of statistics," says Dr. Goring, "is essentially a science of method; and, as applied to criminal man, it may be described as a system of methods whereby comparison, based on a strict anthropometrical survey of the different sets of individuals, may be effective in providing legitimate, simple, and intelligible description of the criminal, and of crime, and of the fundamental inter-relationships of criminality."

The author of the work approaches his inquiry with an open mind regarding the common à priori belief that all men are morally and mentally equal, in the absence of definite pathological cause. This belief is common to all ages. In early days, anti-social conduct was regarded as a sin against the light, i.e., against the teaching of religion and the word of God. The punishment of crime was, therefore, an affair for the ecclesiastical tribunals. The distinction between sin and crime evolved but slowly, and the lay punishments of the Classical Schools were largely affected by the religious law. Later, the anti-social man was regarded as a pathological product—the victim of disease; and it is one of the fashions of to-day to regard him as 'a social product'—the victim of adverse social environment.

All these conceptions are regarded as due to a fixed conventional idea that there was a 'normal' man, who led a good life, and an 'abnormal' man who led a bad life, and this misconception is held to have stood in the way of a scientific view of the nature of criminal man. "Scientifically," according to Dr. Goring, "we can only divide men into 'normal' and 'abnormal' when there is some qualitative difference. 'Normal' is the outcome of the natural laws of existence. This becomes 'abnormal' only when supplanted by some pathological process. Normal never 'merges' into the abnormal, e.g., the natural ranges of vesicular breathing, of normal temperature, of folly, and want of control, never merge into the morbid ranges of pneumonic breathing, fevers and madness. The qualities that have to be considered in relation to crime are not 'abnormal' qualities, but qualities common to all humanity. Law-breakers are not a special breed of human beings differing qualitatively from those who keep the law: any difference there may be between these two human classes is of degree only and not of kind: and, similarly, law-breaking is not different in quality from all other forms of anti-social conduct for which men are not punished, even if they are found out: yet here again there is a vast range of difference in degree. And that is why statistical methods are necessary for the scientific study of the criminal. For only by measurement can difference of degree be evaluated; and statistics is merely a refined instrument for making measurements."

The word 'criminal,' strictly-speaking, only designates the fact that an individual has been imprisoned: that he has committed a crime. The object of this inquiry is to determine whether certain constitutional, as well as environmental, factors play a part in the production of the criminal act. It is impossible to state dogmatically à priori what these factors are, or which of them prevail in the determination of a given act, but it is lawful to assume from the phenomenon of crime that there is a hypothetical character of some kind, a constitutional proclivity, either mental, moral or physical, present, to a certain degree, in all individuals, but so potent in some as to determine for them the fate of imprisonment.

This hypothetical character which, in the absence of a better term, Dr. Goring provisionally calls "the criminal diathesis," is described as a "normal" character, possessed to some extent by all normal people whose differences are of degree only, and not of kind. It is a highly complex unanalysable character which, founded upon, and resulting from, a combination of qualities, some, perhaps inconceivably minute, is best described as a "make-up" comparable to the domesticated or wild "make-up" amongst animals, or to the human "make-up" whereby the sociable being is distinguished from the recluse. Nobody would suppose the gregarious tendency, or the impulse to lead a solitary existence, to be a simple primary quality—a so-called unit character—peculiar to the category it represents; and, similarly, criminality is not a simple heritable entity—a primary instinct to evil, for instance, as Lombroso imagined it to be: it is rather a resultant quality springing from many social and anti-social tendencies, which together form the criminal or non-criminal "make-up" called the "criminal diathesis." It is the degree to which a man is thus "made-up" as a criminal or non-criminal which determines eventually the fate of imprisonment: consequently, the intensity of criminal diathesis is measured by conviction or non-conviction, and by frequency of conviction for crime; and the main object of this inquiry has been to find out the extent to which this "criminal diathesis," as measured by criminal records, is associated with environment, training, stock, and with the physical attributes of the criminal. To this examination, the "biometric" method, under the guidance of its distinguished exponent Professor Karl Pearson, has been applied.

Although only those gifted with high mathematical powers could have originated the minute and abstruse symbolical reasoning at the source of the methods whereby the inter-relationship of these phenomena have been measured and calculated, yet the application of these methods, and of the formulæ which have now been provided, are open to any intelligent worker who has knowledge of arithmetic and of simple mathematics, and the computer's zeal for precision and accuracy. If the results do not command general acceptance, they are fruitful of new ideas, which, by further elaboration, may possibly furnish more light on the problem of crime, and may aid in the direction of administrative methods. At least they furnish an extraordinary example of what industry, and skill, and research, can accomplish in a domain where science, in the past, has asserted itself but slightly.

The question of the existence of a criminal type is regarded as essentially anthropometrical, i.e., it can only be solved by the statistical analysis of a large series of measurements. Anthropometry has, of course, been used as an instrument by criminologists, but its strict application demands more than the crude contrast of mean values which is the most that has been hitherto attempted: in addition to the means, it insists that probable errors should be also calculated and recorded; that a measure of the variability of each series of measurements should be obtained; and that, in every case, effects upon measurement due to differentiation in age, stature, intelligence, &c., of the contrasted populations under measurement should be also estimated and allowed for.

Having, by means of a comparison with regard to thirty-seven representative physical attributes of criminals, distinguished (1) by their conviction for different orders of crime, e.g., thefts, assault, arson, sexual offences, and frauds, (2) by their frequency of reconviction, and (3) by the length of their imprisonment, established the conclusion that criminals are not physically differentiated because they are criminals, but because of difference in age, stature, intelligence, &c., our author proceeds to a comparison between statistics of criminals, as a class, and of the non-criminal public. The absence of any comparative data with regard to many of the physical characters of the law-abiding classes is, of course, fatal to any precise demonstration, but a comparison of the head-length, -breadth, -height, -index, and -circumference in convicts is made with similar statistics of a set of undergraduates of Oxford, Cambridge, and Aberdeen Universities, and of the London University College Staff, with the result that prison inmates, as a whole, approximate closer in head-measurement to the Universities generally than do students of different Universities conform with each other in this regard, and that from a knowledge only of an undergraduate's cephalic measurement, a better judgment could be given as to whether he were studying at an English or Scottish University, than a prediction could be made whether he would eventually become a University Professor, or a convicted felon.

Similar comparison with the general Hospital population and with soldiers (118 non-commissioned officers, and men of the Royal Engineers) establishes a similar conclusion that, so far as head-measurements are concerned, the criminal, and the hospital patient, and the soldier cannot be differentiated.