This idea which corresponds to that great biological law which states the dependence of the function on the nature and capacities of the organ and which makes each individual the result of the innate and acquired conditions of his physiological organism, living in a given environment, so that a biological application may be given to the famous saying: "Tell me what you eat and I will tell you what you are,"--this sublime idea which unfolds before our eyes the majestic drama of history, no longer as the arbitrary succession of great men on the stage of the social theatre, but rather as the resultant of the economic conditions of each people, this sublime idea, after having been partially applied by Thorold Rogers[78] has been so brilliantly expounded and illustrated by Achille Loria,[79] that I believe it unnecessary to say anything more about it. One idea, however, still appears to me necessary to complete this Marxian theory, as I remarked in the first edition of my book: _Socialismo e criminalita_. It is necessary, indeed, to rid this impregnable theory of that species of narrow dogmatism with which it is clothed in Marx and still more in Loria. It is perfectly true that every phenomenon, as well as every institution--moral, juridical or political--is simply the result of the economic phenomena and conditions of the transitory physical and historical environment. But, as a consequence of that law of natural causality which tells us that every effect is always the resultant of numerous concurrent causes and not of one cause alone, and that every effect becomes in its turn a cause of other phenomena, it is necessary to amend and complete the too rigid form that has been given to this true idea. Just as all the psychical manifestations of the individual are the resultant of the organic conditions (temperament) and of the environment in which he lives, in the same way, all the social manifestations--moral, juridical or political--of a people are the resultant of their organic conditions (race) and of the environment, as these are the determining causes of the given economic organization which is the physical basis of life. In their turn, the individual psychical conditions become causes and effect, although with less power, the individual organic conditions and the issue of the struggle for life. In the same way, the moral, juridical and political institutions, from effects become causes (there is, in fact, for modern science no _substantial_ difference between cause and effect, except that the effect is always the latter of two related phenomena, and the cause always the former) and react in their turn, although with less efficacy, on the economic conditions.