What do we learn from the ghost's words (lines 2 -22) about how the catholic faith perceived the afterlife?
In Act I, Scene 5, a ghost appears to Hamlet--it is the spirit of Hamlet's father. The ghost indicates that he has been sent to purgatory to be "purged" of the sins he committed during his life: "I am thy father's spirit,/Doomed for a certain term to walk the night,/And for the day confined to fast in fires/Till the foul crimes done in my days of nature/Are burnt and purged away." (lines 9-13)
Purgatory is a teaching of the Roman Catholic Church, where they believe the soul is sent to be purified. Once the king has been purged of his sins, he will be granted acceptance into Heaven.
I am your father's spirit,
Doomed for a certain time to walk the night,
And during the day I am confined to burn in fires,
Until the evil crimes I had done in my life
Are burnt and purged away. If I were not forbidden
To tell the secrets of my prison house,
I could tell a tale whose lightest word
Would crush your soul, freeze your young blood,
Make your two eyes, like stars, jump from their sockets,
Your knotted and combined hair to separate,
And each particular hair to stand on end
Like quills on the angry porcupine.
But this eternal description must not be given
To ears of flesh and blood. Listen, listen, O, listen!
If you ever loved your dear father —
This conversation with Hamlet's father's ghost tells us about the catholic belief of purging of the sins to receive the afterlife. Purgatory is a process of purification in which souls of those deceased people who had died in a state of graceful demeanor are make ready to rise to Heaven to enjoy a better life.