The epigraph from Dante’s Inferno

The epigraph in The Love Song of J. Alfred Prufrock from Dante’s Inferno:

S’io dredesse che mia reposta fosse
A persona che mai tornasse al mondo,
Questa fiamma staria senza piu scosse.
Ma perciocche giammai di questo fondo
Non torno vivo alcun, s’I’odo il vero,
Senza tema d’infamia ti rispondo. (27.61-66)

Roughly translated to mean that if the speaker knew his words would be taken outside of Hades, he would not have told his story. Since he knows that Dante will not leave, he relates his secrets--known only to the dead.