The Seven P's
Symbolism, Imagery, Allegory
The seven P’s carved onto Dante’s forehead represent seven instances of “peccatum,” the Italian word for “sin” or “wound.” That they’re engraved on Dante’s brow at the entrance of Purgatory makes it pretty clear that they’re an allegory for the journey through each of Purgatory’s seven terraces.
Once Dante has cleared a terrace and purged his soul of the corresponding sin, one P will be erased, easing his passage up into the next terrace. Once his forehead is completely devoid of all the scarlet letters (they’re in blood, remember?), his soul is correspondingly free of sin. Then he is ready for ascent into Heaven.