It remains to consider some twentieth-century theories. These have not been worked out with the same elaboration and systematic detail as those of the past, and as yet one may do no more than sketch them.
An instinctive claim to control natural objects is an individual interest of which the law must take account. This instinct has been the basis of psychological theories of private property. But thus far these theories have been no more than indicated. They might well be combined with the historical theory, putting a psychological basis in place of the nineteenth-century metaphysical foundation. A social-psychological legal history might achieve much in this connection.
Of sociological theories, some are positivist, some psychological and some social-utilitarian. An excellent example of the first is Duguit's deduction from social interdependence through similarity of interest and through division of labor. He has but sketched this theory, but his discussion contains many valuable suggestions. He shows clearly enough that the law of property is becoming socialized. But, as he points out, this does not mean that property is becoming collective. It means that we are ceasing to think of it in terms of private right and are thinking of it in terms of social function. If one doubts this he should reflect on recent rent legislation, which in effect treats the renting of houses as a business affected with a public interest in which reasonable rates must be charged as by a public utility. Also it means that cases of legal application of wealth to collective uses are becoming continually more numerous. He then argues that the law of property answers to the economic need of applying certain wealth to definite individual or collective uses and the consequent need that society guarantee and protect that application. Hence, he says, society sanctions acts which conform to those uses of wealth which meet that economic need, and restrains acts of contrary tendency. Thus property is a social institution based upon an economic need in a society organized through division of labor. It will be seen that the results and the attitude toward the law of property involved are much the same as those which are reached from the social-utilitarian standpoint.
Psychological sociological theories have been advanced chiefly in Italy. They seek the foundation of property in an instinct of acquisitiveness, considering it a social development or social institution on that basis.
Social-utilitarian theories explain and justify property as an institution which secures a maximum of interests or satisfies a maximum of wants, conceiving it to be a sound and wise bit of social engineering when viewed with reference to its results. This is the method of Professor Ely's well-known book on Property and Contract. No one has yet done so, but I suspect one might combine this mode of thought with the civilization interpretation of the Neo-Hegelians and argue that the system of individual property, on the whole, conduces to the maintaining and furthering of civilization—to the development of human powers to the most of which they are capable—instead of viewing it as a realization of the idea of civilization as it unfolds in human experience. Perhaps the theories of the immediate future will run along some such lines. For we have had no experience of conducting civilized society on any other basis, and the waste and friction involved in going to any other basis must give us pause. Moreover, whatever we do, we must take account of the instinct of acquisitiveness and of individual claims grounded thereon. We may believe that the law of property is a wise bit of social engineering in the world as we know it, and that we satisfy more human wants, secure more interests, with a sacrifice of less thereby than by anything we are likely to devise—we may believe this without holding that private property is eternally and absolutely necessary and that human society may not expect in some civilization, which we cannot forecast, to achieve something different and something better.
VI
Contract
Wealth, in a commercial age, is made up largely of promises. An important part of everyone's substance consists of advantages which others have promised to provide for or to render to him; of demands to have the advantages promised which he may assert not against the world at large but against particular individuals. Thus the individual claims to have performance of advantageous promises secured to him. He claims the satisfaction of expectations created by promises and agreements. If this claim is not secured friction and waste obviously result, and unless some countervailing interest must come into account which would be sacrificed in the process, it would seem that the individual interest in promised advantages should be secured to the full extent of what has been assured to him by the deliberate promise of another. Let us put this in another way. In a former lecture I suggested, as a jural postulate of civilized society, that in such a society men must be able to assume that those with whom they deal in the general intercourse of the society will act in good faith, and as a corollary must be able to assume that those with whom they so deal will carry out their undertakings according to the expectations which the moral sentiment of the community attaches thereto. Hence, in a commercial and industrial society, a claim or want or demand of society that promises be kept and that undertakings be carried out in good faith, a social interest in the stability of promises as a social and economic institution, becomes of the first importance. This social interest in the security of transactions, as one might call it, requires that we secure the individual interest of the promisee, that is, his claim or demand to be assured in the expectation created, which has become part of his substance.