Dante is instructed regarding the impossibility of regret in heaven. He has just completed his journey through Purgatory, a mountain with the restored earthly Eden at its top. He is about to depart into the beginning of Paradise and the ascent to God, to “rise to the stars.” This fictional account provides one way of imagining how we can “remain untroubled in our ecstasy” in spite of our history of sin.
Matelda explains to Dante that the water flowing through the terrestrial paradise derives from a single, divine source but moves in two directions, thus forming the river Lethe to one side (left) and the river Eunoe to the other (right) (28.121-33). . . . For the river Lethe, Dante draws on the classical tradition, according to which souls of the dead drink Lethe’s waters to forget their previous life before passing into a new earthly existence. . . . Dante now modifies this conception by limiting Lethe’s power (to only the oblivion of guilty memories of sin), the efficacy of which is seen in his own immersion and subsequent forgetfulness (31.91-102; 33.91-9)*. To complement these Lethean powers of oblivion, Dante invents the river (and word) Eunoe, which means “good memory” in Greek (eu = good; nous = mind): specifically, the recollection of good deeds. After he has tasted the waters, first of Lethe and then of Eunoe, Dante is “cleansed and ready to rise to the stars” (33.145)[1]
The blessed …remain untroubled in their ecstasy…We must first of all remember the action of the two streams of Lethe and Eunoë, of which all souls drink in the Earthly Paradise on their way to Heaven. Lethe destroys all memory of guilt and shame and sin: Eunoë restores the memory of the sin as a historical fact, but the accompanying unhappiness remans forgotten – the sin is remembered only as the glad occasion of God’s gracious mercy and forgiveness.[2]
*Purgatorio 33:88-96[3]
and see that your way is as far from God’s
as that highest heaven, which spins the fastest,
is distant from the earth.’
To that I answered: ‘As far as I remember
I have not ever estranged myself from You,
nor does my conscience prick me for it.’
But if you cannot remember that,’
she answered, smiling, ‘only recollect
how you have drunk today of Lethe,
[1] https://danteworlds.laits.utexas.edu/purgatory/10terrestrialparadise.html
[2] Dorothy L. Sayers, Introductory Papers on Dante: The Poet Alive In His Writings (Eugene, Oregon: Wipf and Stock Publishers, 1954), 60.
[3] Jean Hollander & Robert Hollander, Purgatorio (New York: Anchor Books, 2003), 749.