The most fundamental of class distinctions is that between rich and poor.

That between free and slave, in communities that have slavery, is not at first sight strictly parallel, since there may be a class of poor freemen intermediate between the nobles and the slaves; but it is obvious that in this case, too, private property is really responsible for the mode of grading.

Or sometimes social position may seem to depend primarily on industrial occupation, the Indian caste-system providing an instance in point.

Since, however, the most honourable occupations in the long run coincide with those that pay best, we come back once again to private property as the ultimate source of social rank, under an economic system of the more developed kind.
In this brief sketch it has been impossible to do more than hint how social organization is relative to numbers, which in their turn are relative to the skill with which the food-quest is carried on.

But if, up to a certain point, it be true that the structure of society depends on its mass in a more or less physical way, there is to be borne in mind another aspect of the matter, which also has been hinted at as we went rapidly along.