"Therefore I say unto you: Every sin and every blasphemy shall be forgiven men, except the blasphemy of the Spirit, which shall not be forgiven. For whomsoever shall speak against the Son of Man, it shall be forgiven him: but he that shall speak against the Holy Ghost, it shall not be forgiven him, neither in this world, nor in the world to come." - The Gospel according to Saint Matthew, Chapter XII, vs. 31-2.
Often rinsed by Protestants as the most ludicrous of "non-Scriptural" Catholic ideas, Catholic bloggers From Burke to Kirk and Beyond discusses some very interesting theories for the practical justification of the theology behind Purgatory, in light of the recent child abuse scandals in America. It's also worth noting that some Protestant theologians, including C.S. Lewis, an Ulster-Protestant and Anglican, did eventually come to believe that Purgatory not only existed but was fundamentally necessary to make the entire Christian interpretation of Salvation and eschatology work.