[all reference numbers refer to Part, Canto, and Page respectively].
Cato – Cato the Younger killed himself on earth rather than obey Caesar at Utica. The souls in Purgatory are striving for free will, thus, it is apt that Cato is the custodian of Purgatory “Near me an old man solitary I saw, / In his aspect so much to be revered / That no son owes a father more of awe” (Dante 2.1.31-33). We see a few lines later that Cato was released from Limbus (Limbo) by Christ. This allowed no one to move the blessed by the fate of the damned “The evil stream she swells, by the decree / Made when I was delivered from that bond” (Dante 2.1.88-90). We will find out more about free will from Cato and Marco Lombardo.
Time Telling – In Hell, time is static and atemporal. However, where Hell represents hopelessness, Purgatory represents hope. The souls in Purgatory are on the move, so-to-speak, even if it may take some of them a 1,000 years to ascend to Paradise. Because of this, time still has meaning in purgatory. Further, in Hell time can never eradicate sin, but in Purgatory the course of time is reversed because the divine image may still be restored once enough time in Purgatory erases sin. Time is also the main component of Purgatory because, until one cleanses themselves of all evil dispositions (the seven venal sins), they cannot rise through Purgatory to Paradise.
Lethe - We see a reference to the waters of Lethe in Canto XXXI. The waters of Lethe are from Greek mythology, comprising the river Hades. Drinking from these waters is mandatory in order to forget everything said or done while alive. We see this when Dante falls senseless and recovers to find Matilda taking him across Lethe stream. In regard to his sad memories, Dante is told by Beatrice “Answer, for in thee the sad memories / By the water are not yet discomfited” (Dante 2.31.11-12). Therefore, the waters of Lethe may remove all memories of lif...