e us the certain index of the advent of the new phase of
evolution which Socialism foresees and which it strives to hasten.

To assert the existence of the class-struggle is equivalent to saying
that human society, like all other living organisms, is not a
homogeneous whole, the sum of a greater or smaller number of
individuals; it is, on the contrary, a living organism which is made up
of diverse parts, and their differentiation constantly increases in
direct ratio to the degree of social evolution attained.

Just as a protozoon is almost wholly composed of albuminoid gelatine,
while a mammal is composed of tissues widely varying in kind, in the
same way a tribe of primitive savages, without a chief, is composed
simply of a few families and the aggregation is the result of mere
material propinquity, while a civilized society of the historical or
contemporaneous period is made up of social classes which differ, the
one from the other, either through the physio-psychical constitutions of
their component members, or through the whole of their customs and
tendencies, and their personal, family or social life.

These different classes may be rigorously separated. In ancient India
they range from the _brahman_ to the _sudra_: in the Europe of the
Middle Ages, from the Emperor and the Pope to the feudatory and the
vassal, down to the artisan, and an individual cannot pass from one
class into another, as his social condition is determined solely by the
hazard of birth. Classes may lose their legal character, as happened in
Europe and America after the French Revolution, and exceptionally there
may be an instance of an individual passing from one class into another,
analogously to the endosmose and exosmose of molecules, or, to use the
phrase of M. Dumont, by a sort of "social capillarity." But, in any
case, these different classes exist as an assured reality and they
resist every juridical attempt at leveling as long as the fundamental
reason for their differentiation remains.

It is Karl Marx who, better than any one else, has proved the truth of
this theory by the mass of sociological observations which he has drawn
from societies under the most diverse economic conditions.

The names (of the classes), the circumstances and phenomena of their
hostile contact and conflict may vary with the varying phases of social
evolution, but the tragic essence of history always appears in the
antagonism between those who hold the mono