The allegorical interpretation was again a means of salvation for these last. The _De continentia Virgiliana_ of Fulgentius (sixth century) is a curious monument to this fact. This work made Virgil compatible with the Middle Ages and opened his way to that great reputation which he was destined to attain, as the "gentle sage who knew all things." Even John of Salisbury says of the Roman poet, that "_sub imagine fabularum totius philosophiae exprimit veritatem._"[3] The process of interpretation became fixed in the doctrine of the _four meanings,_ literal, allegorical, moral and anagogic, which Dante afterwards transferred to vernacular poetry. It would be easy to accumulate quotations from mediæval writers, repeating in all keys the theory that art inculcates the truths of morality and of faith and constrains hearts to Christian piety, beginning with those well-known verses of Theodulf: "_In quorum dictis_ (that is to say, in the utterances of the poets) _quamquam sint frivola multa, Plurima sub falso tegmine vera latent,_" and so on, until we reach the doctrines and opinions of our own great men, Dante and Boccaccio. For Dante, poetry "_nihil aliud est quam fictio rhethorica in musicaque posita._"[4] The poet should have a "reasoning" in his verses "under a cloak of figure or of rhetorical colour"; and it would be a shameful thing for him, if, "when asked, he were not able to divest his words of such a garment, in such a way as to show that they possessed a true meaning."[5] Readers sometimes stop at the external vesture alone, and this indeed suffices for those who, like the vulgar, do not succeed in penetrating the hidden meaning. Poetry will say to the vulgar, which does not understand "its argument," what a song of Dante's says at its conclusion, "At least behold how _beautiful_ I am": if you are not able to obtain instruction from me, at least enjoy me as a pleasing thing. Many, indeed, "their beauty more than their goodness will delight," in poems, unless they are assisted by commentaries in the nature of the _Convivio,_ "a light which will allow every shade of meaning to reach them."[6] Poetry was the "gay science," "_un fingimiento_" (as the Spanish poet the Marquis of Santillana wrote) "_de cosas utiles, cubiertas ó veladas con muy fermosa cobertura, compuestas, distinguidas é scandidas, por cierto cuento, pessoé medida._"[7]