English Private Law is presented in two volumes which break on the line between property and obligations. Beyond obligations lies the law of actions, and before property comes the law of persons. Before persons comes Part I, whose single chapter deals with the sources of law. Hence there are five Parts in ail. They are not randomly selected, and they are not ordered by the alphabet. The principal task of this introduction is ta explain the structural scheme which relates these five Parts one ta another and, within the Parts, accounts for the principal subdivisions at lower levels of the hierarchy. The first section is exclusively concerned with that explanation. The second then deals very briefly with the provenance of the scheme, which has a long history, The third turns ta the reasons why such a scheme is necessary. The fourth is concerned with the manner in which the scheme has been applied in these volumes. Finally, at the end comes a conclusion in the nature of a disclaimer and an exhortation. The disclaimer is necessary lest we be thought to believe that this scheme is more than the best currently available hypothesis as ta the structure of our law, and the exhortation urges the necessity of a continuing taxonomy debate, to improve the currently available hypotheses.