The Summa Theologiae ranks among the greatest documents of the Christian Church. It provides the framework for Catholic studies in systematic theology and for a classical Christian philosophy. The purpose, then, of this edition is not narrowly ecclesiastical, but to share with all Christians this treasury of wisdom which is part of their common heritage. Moreover, it consults the interests of many who, without claiming to be believers, appreciate a religious integrity which embodies hardbitten rationalism and who recognise in St Thomas a master of that perennial philosophy which, though not confined to the West, is the foundation on which our civilisation is built. Because of this the editors worked under specific instructions to bear in mind not only the professional theologian, but also the general reader with an interest in the 'reason' in Christianity. The publication of the Latin text along with the English will be reassuring to readers with a smattering of Latin, and has the advantages of permitting the translator somewhat more freedom in adapting the text in translation to the understanding of contemporary minds.