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.