Briefly, then, the universal basis of co-operation is the proportioning of benefits received to services rendered. Without this there can be no physiological division of labor; without this there can be no sociological division of labor. And since division of labor, physiological or sociological, profits the whole and each part; it results that on maintenance of the arrangements necessary to it, depend both special and general welfare. In a society such arrangements are maintained only if bargains, overt or tacit, are carried out. So that beyond the primary requirement to harmonious co-existence in a society, that its units shall not directly aggress on one another; there comes this secondary requirement, that they shall not indirectly aggress by breaking agreements. § 54. But now we have to recognize the fact that complete fulfillment of these conditions, original and derived, is not enough. Social co-operation may be such that no one is impeded in the obtainment of the normal return for effort, but contrariwise is aided by equitable exchange of services; and yet much may remain to be achieved. There is a theoretically possible form of society, purely industrial in its activities, which, though approaching nearer to the moral ideal in its code of conduct than any society not purely industrial, does not fully reach it. For while industrialism requires the life of each citizen to be such that it may be carried on without direct or indirect aggressions on other citizens, it does not require his life to be such that it shall directly further the lives of other citizens. It is not a necessary implication of industrialism, as thus far defined, that each, beyond the benefits given and received by exchange of services, shall give and receive other benefits. A society is conceivable formed of men leading perfectly inoffensive lives, scrupulously fulfilling their contracts, and efficiently rearing their offspring, who yet, yielding to one another no advantages beyond those agreed upon, fall short of that highest degree of life which the gratuitous rendering of services makes possible. Daily experiences prove that every one would suffer many evils and lose many goods did none give him unpaid assistance. The life of each would be more or less damaged had he to meet all contingencies single-handed. Further, if no one did for his fellows anything more than was required by strict performance of contract, private interests would suffer from the absence of attention to public interests. The limit of evolution of conduct is consequently not reached, until, beyond avoidance of direct and indirect injuries to others, there are spontaneous efforts to further the welfare of others.