“The poetic splendor of the Inferno breaks upon the reader as soon as he opens the first pages of the Comedy; but it is often obscured by historical allusions, astronomical circumlocutions, and terms of mediaeval science or philosophy, which darken and at times quench its light. These obstacles, however, soon begin to yield to patient study, and what threatened to choke the flame catches fire from it and in its turn flings light into every corner of the world in which Dante lived and thought.
Meanwhile, earlier or later as the case may be, the reader becomes aware of an underlying purpose and significance, seldom obtruded but always present, that gives unity and direction to the movement of the whole poem, breathing into it a vital spirit of its own and appealing for its interpretation to no other lore than such as knowledge of ourselves and observation of life can give us.
Presently, when we grow familiar with the Purgatorio and the Paradiso, the Inferno, in spite of its direct and arresting grip upon our imagination, reveals itself as a beginning that must be read in the light of the middle and the end if we are to understand it truly; and we begin to feel, perhaps gropingly, for the organic relation of the parts to the whole. The misleading suggestion will probably present itself to us, at this point, that the first Cantica of the Comedy is the foundation on which the whole structure stands, and that the way to heaven lies through hell. There is indeed a sense in which this is true, but we can never rightly grasp it till we have realized the deeper sense in which it is false. This is the first point to which we must turn our attention” (P. H. Wickstead, From Vita Nuova to Paradiso p 3-4).