Commentary Inf IV 102
For a review of the various sorts of discomfort among the commentators occasioned by Dante's promotion of his own poetic career in this verse (some going so far as to insist that he displays humility here rather than pride) see Mazzoni (Mazz.1965.1), pp. 147-154. This is not to take issue with the position taken by Sarolli, shared by the great French Dante scholar Etienne Gilson, that Dante in fact generally does present himself as humble in taking on the burden of this poem in order to do the work of God (Saro.1971.1, p. 385n.). However, it is clear that Dante is putting himself in very good company on the basis of very little accomplishment: a series of lyrics, the Vita nuova, two unfinished treatises, and three cantos of the Comedy. His daring is amazing. However, we ought to consider that most of his readers today will readily agree that he is not only justly included in this company of the great poets of all time between Homer and Dante, but is one of its foremost members. It was a dangerous gesture for him to have made. It is redeemed by his genius. Taaffe translates Biagioli's response in precisely this mode (Taaf.1822.1, p. 252): 'Who but will admire, if not entirely blind, the modesty of our poet in calling himself only the sixth in a company, where he is really on a perfect equality with the first?'

For a possible source for this verse see Gmel.1966.1, p. 91: Ovid's Tristia, IX, x, 54, where that poet makes himself fourth in the line of poets after Tibullus, Gallus, and Propertius. And we should look ahead to [Purg XXI 91] when the inclusion of Statius will make Dante not the sixth but the seventh (a more propitious number?) in this group. That there are forty named or otherwise identified inhabitants in Limbo is probably not accidental (the five poets and the thirty-five souls later observed in the precincts of the noble castle). In one tradition of medieval numerology the 'number' of man is four (of God, three). In a widely practiced mode of medieval 'counting,' 40 = 4 + 0 = 4.