Did Dante, who so valued time, have any precise idea as to how time is perceived? The answer must be found in Purg. IV.1-18, where the protagonist's failure to notice the passage of time while attending to Manfredi, "udendo quello spirto e ammirando," is elaborately foregrounded. Lines 10-12, in particular, suggest that some single faculty is responsible for time-perception:

ch'altra potenza è quella che l'ascolta,
e altra è quella c'ha l'anima intera:
questa è quasi legata e quella è sciolta.

Unfortunately, the reader who surveys the commentaries for an explanation of these lines will traverse centuries of critical confusion, arriving at the modern consensus view which asks us to believe that Dante's intellect is inoperative as he listens to Manfredi, despite the intellectual nature of admiratio, and that it is the intellect which perceives time, despite the fact that Aristotle, Albert and Aquinas were in no doubt, as we shall see, that time-perception is a function of the sensitive soul. (1)

The soul was understood to be the principle of activity in living things. In support of the doctrine that human beings have one soul with several powers or faculties, not several souls, medieval theologians sometimes adduced a fact of common experience: when the activity of one faculty is so intense that it completely absorbs the attention of the soul, the activity of one or more other faculties is impeded, either partially or totally. This was taken as proof that the faculties had one principle, and therefore one soul.(2) The phenomenon is often concisely described in a binary opposition, contrasting (first) an active power which is the focus of the soul's attention with (second) another power or powers that are impeded because attention has been withdrawn. A typical example is: "quando una potentia intenditur in suo actu, altera in suo actu remittitur, vel etiam totaliter impediatur." (3)

 Such is the conceptual and syntactic foundation of the passage as a whole. However, Dante complicates matters with an inversion which throws the commentators into confusion. He begins with the standard opposition as a general statement of the relevant psychological experience, with the active power mentioned first and the impeded powers second (1-4). He then gives the specific case of the failure to perceive time, in which (stated first) active external senses attract the soul's complete attention, while (stated second) the faculty which perceives time fails to do so (7-9). Next, he explains that this is because the contrasted powers are in two different conditions, one "legata" and the other "sciolta" (10-12). It is clear that the power which Dante mentions second ("quella c'ha l'anima intera," 11) is the one which has the soul's complete attention and is therefore fully operative, so that the one which he mentions first ("quella che l'ascolta," 10) must be the impeded power which would otherwise perceive time. The usual order has therefore been inverted. Dante then (12-16) returns to that usual order when he reports his own "esperïenza vera" of the phenomenon: hearing and wondering at Manfredi's words (free activity first), he was so preoccupied that he failed to notice that the Sun had moved fifty degrees, i.e., over three hours had passed (impeded activity second). The inversion in lines 10-12 is natural, given that the theme is time-perception, for it makes "l'ascolta" follow immediately from "'l tempo." The use of ascoltare with the meaning "to pay heed to" has been a source of confusion, given the forms of udire in lines 7 and 14. To Parodi's justification of such a reading of the verb, one could add the famous "'l sol tace" (Inf. I.60). (4)

  Another source of critical disarray is the fact that very few of the commentators seem to be aware that "legata" and "sciolta" are used with the quasi-technical meanings which were given to ligare/ligatum and solvere/solutum in medieval psychology. Ligare and solvere were used metaphorically, and consistently, to signify the impeding and the freeing, respectively, of a power's activity.(5) "Legata" therefore describes the impeded faculty which should perceive time, and "sciolta" the faculties of hearing or listening.

However, since it is almost universally assumed that "questa" and "quella" mean "the latter" and "the former" respectively, the commentators connect "questa...legata" with the active power which Dante mentions second (11) and "quella...sciolta" with the impeded one which he mentions first (10), and are therefore obliged to distort the meanings of those adjectives. This complication is removed when one realises that Dante is using questo and quello in correlation to mean quite the opposite, that is, "the former" and "the latter" respectively, just as he does in Purg. XXV.52-54.(6) In Classical and Medieval Latin, hic and ille could be used in this way.(7) In other words, the power that perceives time is "questa...legata," while the power of hearing or of vision is "quella...sciolta."

Finally, and incredibly, I have been unable to find any reference in the commentaries to the fact that medieval psychology assigned the perception of time not to the intellect but to a precise faculty of the sensitive soul. Time, it was argued, is the measure or magnitude of movement, and is therefore inseparable from magnitude (cf. "cinquanta gradi") and movement (cf. "salito era," 15). The faculty which perceives time must therefore be the one which perceives and collates these two common sensibles, the one where all sensations are collated to result in a completed perception, and that faculty is the sensus communis, an internal sense to be found in both animals and humans.(8) What the intellect does with this sensory input is another matter.

Dante is saying, then, that when the attention of the soul is completely drawn to a power such as sight or hearing, then time passes unperceived, because those senses are freely operating, but the internal sensus communis is impeded with respect to the perception of time. While listening to Manfredi, wonder at the substance of what he was hearing so occupied the attention of his mind that his sense of hearing and his intellect were intensely busy, leaving his sensus communis disabled with respect to time-perception. In short, Dante's intellect was so engaged with the input of an external sense, that one of his internal senses failed to do its job properly. If this seems contrived, it should be noted that the very same thing subsequently happens twice to the protagonist, the only difference being that the impeded internal sense in those cases is memory (see Purg. XXXIII.124-126 and Par. III.7-9).

Nonetheless, since Dante valued time so highly, the fact that he never mentions the sensus communis specifically in this regard suggests that he may not have been aware that this particular faculty was thought to be responsible for time-perception, believing only that it was some faculty other than the external senses and the intellect. In any case, the syntactic and conceptual structure of lines 10-12, as I have attempted to describe it, can accommodate either possibility. Bearing in mind the correct meanings of "legata" and "sciolta," this structure would be self-evident if Dante had written

ch'altra potenza è questa che l'ascolta,
e altra è quella c'ha l'anima intera:
questa è quasi legata e quella è sciolta.

This is the text we would have if Petrocchi, in his edition of the Commedia, had accepted the variant in Vatican Library Urbinate Latino 366, the only manuscript in the "antica vulgata" group that has "questa" instead of "quella" in line 10. Federico Sanguineti bases his new critical edition on this manuscript, but in this case he does not adopt its reading, presumably because he could see no good reason to do so.(9) That part of my argument which attempts to clarify the syntax of the passage suggests that there is every reason, rendering itself redundant in the process.