Commentary Purg XXXI 103-108

The four nymphs represent the four cardinal virtues (Justice, Prudence, Temperance, and Fortitude) in their primal form, i.e., as they were infused in Adam and Eve (and not acquired, as they have had to be ever after).  God created the first humans, and no others, in this state.  They are 'nymphs' in that, like some classical nymphs, they inhabit a woodland landscape (Lombardi [DDP Lombardi.Purg.XXXI.106]).  The stars they are in heaven are probably (there is debate about this) identical with those we saw in [Purg I 23] (also referred to in [Purg I 37-39] and [Purg VIII 91]), irradiating the face of Cato with their light.  Dante thus seems to suggest that both Cato and Beatrice are of such special virtue that it seems that original sin did not affect them -- a notion that could only be advanced in the sort of suggestive logic possible in poetry, for it is simply heretical.  Dante never did say (or would have said) such a thing in prose.

      The exact sense in which they served as the handmaids of Beatrice before she lived on earth is less easily determined.  For two similar views of the problem see Singleton (Sing.1958.1), pp. 159-183, and Mazzoni (Mazz.1965.2), pp. 82-86.  Both link the infused cardinal virtues to Beatrice's special role on earth, reflected in such passages as [Inf II 76-78], where she is addressed by Virgil as 'donna di virtù' (lady of such virtue that by it alone / the human race surpasses all that lies / within the smallest compass of the heavens).

      Botticelli-like (as in his Primavera, surely shaped by this scene), the four dancing maidens make a composite sign of the cross with their upraised arms, which join over Dante's head.  All redeemed sinners leave the garden of Eden on their way to glory in the moral condition that marked the creation of the first humans, before the Fall: primal innocence.