Dante Alighieri, from Book Two of The Convivio, on "The Allegory of the Poets"

[2] I say ... that the interpretation should be both literal and allegorical. For the understanding of this, it should be realized that texts can be understood and should be explicated primarily on four levels.

[3] The first of these is called the literal level, the level which does not extend beyond the letter of the fictive discourse, which is what the fables of the poets are.

The second is called allegorical, and is hidden under the cloak of these fables, a truth disguised under a beautiful lie; as for example when Ovid says that Orpheus with his lyre made the wild beasts tame, and caused the trees and the stones to move, this means that the wise man with the instrument of his voice makes cruel hearts tame and humble, and causes the wills of those who do not have a life of learning and art to be moved (for those who do not possess the life of reason are like stones).

[4] . . . Of course, the theologian understand this sense in another way than do the poets. But because my purpose is to follow the mode of the poets, I understand the allegorical sense as it is used by poets.

[5] The third sense is called the moral, and it is this one which teachers should seek out with most diligence when going through texts, because of its usefulness to them and to their pupils. One may discover, for example, from the Gospel, that when Christ went up to the mountain to be transfigured, he took only three of the twelve disciples with him. This may be interpreted morally to mean that in the most secret affairs we should have few companions.

[6] The fourth sense is called the anagogical, or the "sense beyond." This sense occurs when a spiritual interpretation is to be given a test which, even though it is true on the literal level, represents the supreme things belonging to eternal glory by means of the things it represents. It may be perceived in that song of the Prophet which says that, in the departure of the people of Israel from Egypt, Judea was made holy and free.

[7] For even though the literal truth of this passage is clear, what it means spiritually is no less true, that in the departure of the soul from sin, it is made holy and free in its power.

[8] In bringing out this meaning, the literal sense should always come first, it being the meaning in which the others are contained and without which it would be impossible and irrational to come to an understanding of the others, particularly the allegorical.

[9] It would be impossible because, in the case of anything which has an outside and an inside, it is impossible to come to the inside without first coming to the outside. Thus, since in a text the literal meaning is always the outside, it is impossible to come to the others, particularly the allegorical, without first coming to the literal.