The third sense is termed Moral; and this is that which the readers ought intently to search for in books, for their own advantage and for that of their descendants; as one can espy in the Gospel, when Christ ascended the Mount for the Transfiguration, that, of the twelve Apostles, He took with Him only three. From which one can understand in the Moral sense that in the most secret things we ought to have but little company.
The fourth sense is termed Mystical, that is, above sense, supernatural; and this it is, when spiritually one expounds a writing which even in the Literal sense by the things signified bears express reference to the Divine things of Eternal Glory; as one can see in that Song of the Prophet which says that by the exodus of the people of Israel from Egypt Judaea is made holy and free. That this happens to be true according to the letter is evident. Not less true is that which it means spiritually, that in the Soul’s liberation from Sin (or in the exodus of the Soul from Sin) it is made holy and free in its powers.
But in demonstrating these, the Literal must always go first, as that in whose sense the others are included, and without which it would be impossible and irrational to understand the others. Especially is it impossible in the Allegorical, because, in each thing which has a within and a without, it is impossible to come to the within if you do not first come to the without. Wherefore, since in books the Literal meaning is always external, it is impossible to reach the others, especially the Allegorical, without first coming to the Literal. Again, it is impossible, because in each thing, natural and artificial, it is impossible to proceed to the form without having first laid down the matter upon which the form should be. Thus, it is impossible for the form of the gold to come, if the matter, that is, its subject, is not first laid down and prepared; or for the form of the ark to come, if the material, that is, the wood, be not first laid down and prepared. Therefore, since the Literal meaning is always the subject and the matter of the others, especially of the Allegorical, it is impossible to come first to the meaning of the others before coming to it. Again, it is impossible, because in each thing, natural and artificial, it is impossible to proceed unless the foundation be first laid, as in the house, so also in the mind. Therefore, since demonstration must be the building up of Knowledge, and Literal demonstration must be the foundation of the other methods of interpreting, especially of the Allegorical, it is impossible to come first to the others before coming to that. Again, if it were possible that it could be so ordered, it would be irrational, that is, out of order; and, therefore, one would proceed with, much fatigue and with much error. Hence, as the Philosopher says in the first book of the Physics, Nature desires that we proceed in due order in our search for knowledge, that is, by proceeding from that which we know well to that which we know not so well; so I say that Nature desires it, inasmuch as this way to knowledge is innate in us; and therefore, if the other meanings, apart from the Literal, are less understood—which they are, as evidently appears—it would be irrational to demonstrate them if the Literal had not first been demonstrated.