90-120. Quando mi diparti . . canoscenza: Among possible sources for Dante's conception of Ulysses is a passage in Cicero, De fin. V, xviii, 48-49:

Videamus animi partes, quarum est conspectus illustrior; quae quo sunt excelsiores, eo dant clarior indicia naturae. Tantus est igitur innatus in nobis cognitionis amor et scientiae ut nemo dubitare possit quin ad eas res hominum natura nullo emolumento invitata rapiatur. Videmusne ut pueri ne verberibus quidem a contemplandis rebus perquirendisque detereantur? ut pulsi recurrant? ut aliquid scire se gaudeant? ut id aliis narrare gestiant? ut pompa, ludis atque eiusmodi spectaculis teneantur ob eamque rem vel famem et sitim perferant? Quid vero? qui ingeniuis studiis atque artibus delectantur, nonne videmus eos nec valetudinis nec rei familiaris habere rationem omniaque perpeti ipsa cognitione et scientia captos et cum maximis curis et laboribus compensare eam quam ex discendo capiant voluptatem? Mihi quidem Homerus huiusmodi quiddam vidisse videtur in iis quae de Sirenum cantibus finxerit. Neque enim vocum suavitate videntur aut novitate quadam et varietate cantandi revocare eos solitae qui praetervehebantur, sed quia multa se scire profitebantur, ut homines ad earum saxa discendi cupiditate adhaerescerent. Ita enim invitant Ulixem . . . Vidit Homerus probari fabulam non posse si cantiunculis tantus irretitus vir teneretur; scientiam pollicentur, quam non erat mirum sapientiae cupido patria esse cariorem. Atque omnia quidem scire cuiuscumquemodi sint cupere curiosorum, duci vero maiorum rerum contemplatione ad cupiditatem scientiae summorum virorum est putandum.

Let us consider the parts of the mind, which are of nobler aspect. The loftier these are, the more unmistakable indications of nature do they afford. So great is our innate love of learning and of knowledge, that no one can doubt that man's nature is strongly attracted to these things even without the lure of any profit. Do we [not] notice how children cannot be deterred even by punishment from studying and inquiring into the world around them? Drive them away, and back they come. They delight in knowing things; they are eager to impart their knowledge to others; pageants, games and shows of that sort hold them spell-bound, and they will even endure hunger and thirst so as to be able to see them. Again, take persons who delight in the liberal arts and studies; do we not see them careless of health or business, patiently enduring any inconvenience when under the spell of learning and of science, and repaid for endless toil and trouble by the pleasure they derive from acquiring knowledge? For my part I believe Homer had something of this sort in view in his imaginary account of the songs of the Sirens. Apparently it was not the sweetness of their voices or the novelty and diversity of their songs, but their professions of knowledge that used to attract the passing voyagers; it was the passion for learning that kept men rooted to the Sirens' rocky shores. This is their invitation to Ulysses . . . . Homer was aware that his story would not sound plausible if the magic that held his hero immeshed was merely an idle song! It is knowledge that the Sirens offer, and it was no marvel if a lover of wisdom held this dearer than his home. A passion for miscellaneous omniscience no doubt stamps a man as a mere dilettante; but it must be deemed the mark of a superior mind to be led on by the contemplation of high matters to a passionate love of knowledge.

Cicero continues with many illustrious examples of men who felt an overwhelming desire for knowledge. See Horace, Epistles I, ii, 17-26:

Rursus, quid virtus et quid sapientia possit, utile proposuit nobis exemplar Ulixen, qui domitor Troiae multorum providus urbes et mores hominum inspexit, latumque per aequor, dum sibi, dum sociis reditum parat, aspera multa pertulit, adversis rerum immersabilis undis. Sirenum voces et Circae pocula nosti; quae si cum sociis stultus cupidusque bibisset, sub domina meretrice fuisset turpis et excors, vixisset canis immundus vel amica luto sus.

Again, of the power of worth and wisdom he has before us an instructive pattern in Ulysses, that tamer of Troy, who looked with discerning eyes upon the cities and manners of many men, and while for self and comrades he strove for a return across the broad seas, many hardships he endured, but could never be overwhelmed in the waves of adversity. You know Sirens' songs and Circe's cups; if, along with his comrades, he had drunk of these in folly and greed, he would have become the shapeless and witless vassal of a harlot mistress--would have lived as an unclean dog or a sow that loves the mire.

Compare Seneca, Epist. mor. LXXXVIII, 7:

Quaeris, Ulixes ubi erraverit, potius quam efficias, ne nos semper erremus? Non vacat audire, utrum inter Italiam et Siciliam iactatus sit an extra notum nobis orbem, neque enim potuit in tam angusto error esse tam longus; tempestates nos animi cotidie iactant et nequitia in omnia Ulixis mala inpellit.

Do you raise the question, "Through what regions did Ulysses stray?" instead of trying to prevent ourselves from going astray at all times? We have no leisure to hear lectures on the question whether he was sea-tost between Italy and Sicily, or outside our known world (indeed, so long a wandering could not possibly have taken place within its narrow bounds); we ourselves encounter storms of the spirit, which toss us daily, and our depravity drives us into all the ills which troubled Ulysses.

Singleton, Charles. Inferno 2: Commentary.Princeton, New Jersey: Princeton University Press, Bollingen Series LXXX., 1970.