Didascalicon, Book V: the senses of Scripture and the three kinds of readers
Chapter II. On the threefold understanding
First of all it is to be understood that divine Scripture has a threefold manner of understanding, that is history, allegory and tropology. Not all that is found in the divine utterance is to be twisted to this threefold interpretation, so that each be believed to contain history, allegory and tropology at once. Although this could fittingly be assigned in many places, yet to observe it everywhere is either difficult or impossible. For just as in harps and musical instruments of this sort not all that is touched resounds with song, but only the strings, yet the rest in the whole body of the harp was made so that there might be somewhere to connect and stretch those strings which the player is to use for the sweetness of the tune, so in the divine utterances some things are set down which are meant to be understood only spiritually; some serve the gravity of morals; some are also said according to the simple sense of history; and some can be fittingly expounded historically, allegorically and tropologically at once. Hence in a wonderful manner all divine Scripture has been so fittingly fitted and disposed in its parts by the wisdom of God that whatever is contained in it either, in the manner of strings, sounds the sweetness of spiritual understanding, or, through the series of history and the solidity of the letter, containing the sayings of mysteries scattered here and there and as it were joining them into one, like a hollow wood over stretched strings joins them together, and receiving their sound into itself, brings back to the ears a sweeter sound, which not only the string has produced but the wood also has shaped by the measure of its body. So also honey in the comb is more pleasing. And whatever is sought with greater exercise is also found with greater desire. We must therefore so treat divine Scripture that we do not seek history everywhere, nor allegory everywhere, nor tropology everywhere; but assign each in its own place suitably, as reason demands. Yet often in one and the same letter all can be found; as the truth of history may also insinuate something mystical through allegory, and likewise show through tropology what is to be done.