Thomas Aquinas begins the Summa Theologiae with the question de sacra doctrina, qualis sit et ad quae se extendat. Readers of this question often assume that he is here asking about the nature of Christian theology. This assumption is open to question and in what follows I shall briefly explain why that is so and what Aquinas actually does mean by sacra doctrina.
I
The most obvious reason for refusing to equate sacra doctrina in Aquinas with ‘theology’, as that word is commonly used, is that much that would now pass for theology would not be recognised by Aquinas as sacra doctrina. In most modern discsssions, ‘theology’ does not mean ‘teaching we agree with’. It means what people who earn their living as theologians say or write. On that basis, editors and librarians, whether Christian or not, will class as theology the views of people as different as Augustine and Troeltsch, Luther and Cajetan, Schillebeeckx and Ratzinger. These pairs of authors, and others one could mention, have wildly divergent things to say, but all of it counts as theology. For Aquinas, however, not all of it would constitute sacra doctrina. That, for him, is nothing but true teaching. For him, sacra doctrina is indeed ‘teaching we agree with’. Or, more precisely, it is teaching we ought to agree with. As we read in la, 1,1, it is something revealed by God.
In the second place, ‘theology’ does not translate sacra doctrina. The proper translation is ‘holy teaching’ or ‘sacred doctrine’.