The positive theory of penal substitutes, apart from any particular example, aims precisely at furnishing a mental discipline for legislators, and bringing home to them the duty of constant reinforcements of social prevention, no matter how difficult it may be, before the evil comes to a head, and forces them too late to a course of repression which is as easy as it is fallacious. No doubt it is vexatious and difficult, even in private life, to be perpetually living up to rules of health; and it is easier, if more dangerous, to forget them, and to fly, when the mischief declares itself, to drugs which are too frequently deceptive; but it is just the want of forethought, both public and private, which it is so important to overcome. And as hygienic science was not possible as a theory or as a practice until after <p 135>the experimental observations and physio-pathology on the causes of disease, especially of epidemic and infectious diseases, together with the discoveries of M. Pasteur, who created bacteriology; so social hygiene as against crime was only possible as a theory, and will not be so as a practice, till the diffusion of the facts of biology and criminal sociology relating to the natural causes of crime, especially of occasional crime. The great thing is to be convinced that, for social defence against crime, as for the moral elevation of the masses of men, the least measure of progress with reforms which prevent crime is a hundred times more useful and profitable than the publication of an entire penal code. When a minister introduces a law, for instance, on railways, customs duties, wages, taxation, companies, civil or commercial institutions, there are few who think of the effect which these laws will have on the criminality of the nation, for it is imagined that sufficient has been done in this respect by means of reforms in the penal code. In the social organism, on the other hand, as in individuals, there is an inevitable solidarity, though frequently concealed, between the most distant and different parts.