4. _Private property may now be justified mainly on the grounds of social expediency._ This is a broad explanation under which can be brought the many varying conditions; but it has the fault of a broad explanation, that it needs be further explained. Conceding that private property works hardship to the individual in many cases, it must be justified on the ground that, on the whole, it furthers the progress of society. Private property is looked upon by some as merely reflecting or expressing the economic inequalities of men; the man poor in ability is the man poor in property. It is looked upon by others as exaggerating, indeed at times reversing, the economic abilities of men. In general, it must be judged by this test: Does it further the welfare of society better than would any alternative plan for the control of economic wealth? The question is not whether it is faultless, for no human institution is so. Nor must it be assumed that property is a fixed and uniform mode of control; there are many kinds of property. Different parts of wealth may be treated in different ways: there may be private property in wagons, and public property in roads; private property in houses, and public property in forests; private property in automobiles, and, in some countries, public property in railway-carriages. But any rule of property, like any other workable human law, must be applicable to all individuals that meet the conditions. Hence any human institution must be judged by its average working, not by exceptional cases. The very acceptance of the theory of social expediency implies the need of a readjustment of the institution of private property; for private property, as it is found to-day, is complicated by many historical accidents. Survivals of ancient injustice and relics of feudal institutions that rest on no vital reason remain in our new country as well as in the older ones. The limits of property in many respects are determined, not according to the logic of expediency, but by the social inertia which often governs succeeding generations. § III. LIMITATIONS OF THE RIGHT OF PRIVATE PROPERTY [Sidenote: Public interests limiting property rights]