Didascalicon, Book VI: how Scripture is to be read
Chapter II. On the order that is in the disciplines
First, then, the reader of divine things ought to consider this order which is sought in the disciplines, among history, allegory and tropology: which of these precedes the others in the order of reading. In this it is not useless to recall what is seen to be done in buildings, where first the foundation is laid, then the structure is built upon it; at last, the work being completed, the house is clothed with a color laid over it.