Commentary Inf VII 118-126

Those who are punished under the surface of the Styx are, in this formulation (see C.Inf.VII.109-114), what St. Thomas characterizes as Aristotle's second set of the wrathful, the amari, or 'bitter.' These people kept their anger in, suffering gravely within themselves (as opposed to the choleric, quick to vent their anger in insults and blows). Dante's inventive representation of this kind of wrath shows its exemplars as experiencing the 'muddy' or 'smoky' sensation of stifled anger. For Thomas's own distinction, overlooked by some who deal with this passage, between acedia (tristitia de bono spirituali as capital vice and as form of anger, see Casagrande (Casa.2002.1). And, for the relation between speech being cut off and particularly fervid anger, as discussed both by Albert the Great and St. Thomas, see Casagrande, p. 70.