It is thanks to it that students of the philosophy of law and sociology are able to determine the true nature and functions of the _State_ which, as it is nothing but "society juridically and politically organized," is only the secular arm used by the class in possession of the economic power--and consequently of the political, juridical and administrative power--to preserve their own special privileges and to postpone as long as possible the evil day when they must surrender them. The other sociological theory by which Karl Marx has truly dissipated the clouds which had ere then darkened the sky of the aspirations of socialism, and which has supplied scientific socialism with a political compass by the use of which it can guide its course, with complete confidence and certainty, in the struggles of every-day life, is the great historical law of _class struggles_.[81] ("The history of all hitherto existing society is the history of class struggles." Communist Manifesto. Marx and Engels. 1848.) If it is granted that the economic conditions of social groups, like those of individuals, constitute the fundamental, determining cause of all the moral, juridical and political phenomena, it is evident that every social group, every individual will be led to act in accordance with its or his economic interest, because the latter is the physical basis of life and the essential condition of all other development. In the political sphere, each social class will be inclined to pass laws, to establish institutions and to perpetuate customs and beliefs which, directly or indirectly subserve its interests. These laws, these institutions, these beliefs, handed down by inheritance or tradition, finally obscure or conceal their economic origin, and philosophers and jurists and often even the laity defend them as truths, subsisting by virtue of their own intrinsic merits, without seeing their real source, but the latter--the economic sub-stratum--is none the less the only scientific explanation of these laws, institutions and beliefs. And in this fact consists the greatness and strength of the perspicacious conception of the genius of Marx.[82] As in the modern world there are now but two classes, with subordinate varieties,--on the one side the workers to whatever category they belong, and on the other the property owners who do not work,--the socialist theory of Marx leads us to this evident conclusion: since political parties are merely the echoes and the mouth-pieces of class interests--no matter what the subvarieties of these classes may be--there can be substantially only two political parties: the socialist labor party and the individualist party of the class in possession of the land and the other means of production.