A social interest in the security of acquisitions and a social interest in the security of transactions are the forms of the interest in the general security which give the law most to do. The general safety, peace and order and the general health are secured for the most part by police and administrative agencies. Property and contract, security of acquisitions and security of transactions are the domain in which law is most effective and is chiefly invoked. Hence property and contract are the two subjects about which philosophy of law has had the most to say. In the law of liability, both for injuries and for undertakings, philosophical theories have had much influence in shaping the actual law. If they have grown out of attempts to understand and explain existing legal precepts, yet they have furnished a critique by which to judge those precepts, to shape them for the future and to build new ones out of them or upon them. This is much less true of philosophical theories of property. Their rôle has not been critical or creative but explanatory. They have not shown how to build but have sought to satisfy men with what they had built already. Examination of these theories is an illuminating study of how philosophical theories of law grow out of the facts of time and place as explanations thereof and then are given universal application as necessarily explanatory or determinative of social and legal phenomena for all time and in every place. It has been said that the philosophy of law seeks the permanent or enduring element in the law of the time and place. It would be quite as true to say that it seeks to find in the law of the time and place a permanent or enduring picture of universal law.