From the extraordinary nature of his material, Dante needed for the form of his creations in detail, some kind of credentials which only the Science of his time could give, and which for him are, so to speak, the Mythology and the general basis, which supports the daring edifice of his inventions. But even in the details he remains trite to his design of being allegorical, without ceasing to be historical and poetical. Hell, Purgatory and Paradise are, as it were, only his system of Theology in its concrete and architectural development. The proportion, number and relations which he observes in their internal structure were prescribed by this science, and herein he renounced intentionally the freedom of invention, in order to give, by means of form, necessity and limitation to his poem, which in its materials was unlimited. The universal sanctity and significancy of numbers is another external form upon which his poetry rests. So in general the entire logical and syllogistic lore of that age, is for him only form, which must be granted to him, in order to attain to that region in which his poetry moves. And yet in this adherence to religious and philosophical notions, as the most universally interesting thing which his age offered, Dante never seeks an ordinary kind of poetic probability; but rather renounces all intention of flattering the baser senses. His first entrance into Hell takes place, as it should take place, without any unpoetical attempt to assign a motive for it or to make it intelligible, in a condition like that of a Vision, without however any intention of making it appear such. His being drawn up by Beatrice’s eyes, through which the divine power is communicated to him, he expresses in a single line: what is wonderful in his own adventures he immediately changes to a likeness of the mysteries of religion, and gives it credibility by a yet higher mystery, as when he makes his entrance into the moon, which he compares to that of light into the unbroken surface of water, an image of God’s incarnation. To show the perfection of art, and the depth of purpose which was carried even into the minor details of the inner structure of the three worlds, would be a science in itself. This was recognized shortly after the poet’s death by his nation, in their appointing a distinct Lectureship upon Dante, which was first filled by Boccaccio.