Commentary Purg XVII 82-87

Just as the poem is now entering its second half and this cantica arriving at its midpoint, so the experience of the repentance of the seven capital vices has come to its central moment with Sloth.  From Dante's question and Virgil's answer we also understand that there is a gulf separating the vices below, all of which begin in the love of what is wrongful, from the rest, all of which result from insufficient or improper desire to attain the good.  The sin purged here is called acedia in Latin and accidia in Italian.  (For a lengthy consideration see Wenzel's book [Wenz.1967.1]; see also Andrea Ciotti's entry, which sometimes takes issue with Wenzel, 'accidia e accidiosi' in ED.1970.1; for a wider view of acedia see Kuhn [Kuhn.1976.1], with special reference to Dante on pp. 56-59).  In the poem, the word will appear in the next canto, used retrospectively to indicate the sin repented here ([Purg XVIII 132]); however, in adjectival form it was present earlier ([Inf VII 123] and see C.Inf.VII.118-126).  Scartazzini (DDP Scartazzini.Purg.XVII.85-86) brings St. Thomas (ST I.lxiii.2) into play as the one who affords a clear understanding of this sin, a kind of spiritual torpor accompanied by (or even caused by) physical weariness: 'Acedia vero est quaedam tristitia qua homo redditur tardus ad spirituales actus propter corporalem laborem' (Acedia is in fact a certain sadness by which a man is drawn only slowly to his spiritual actions because of physical fatigue).