My copy of Why do Catholics Do That?, by Kevin Orlin Johnson, says
I recommend this book for other similar questions, as it is an easier read than the Catechism.
To address indulgences, the book says that an indulgence can take away a “temporal punishment” for sin, but only as long as the sin has been forgiven. Meaning, that you’ve already been to Reconciliation and done your penance asked of you.
To put all this in perspective – how many Catholics, or other Christians, still take the idea of Hell seriously?
From George Orwell’s “As I Please” column in the Tribune, April 14, 1944:
(A footnote from the book I’m using, The Collected Essays, Journalism and Letters of George Orwell, Vol. 3 (New York and London: Harcourt Brace Jovanovich, 1968), says, "Orwell acknowledged later that he was mistaken in attributing these verses to Chesterton and that they were by A.M. Currie and had appeared in G.K. Chesterton’s paper, G.K.'s Weekly.)
Now, Orwell was writing in Britain, where the level of religiosity has for a long time been much lower than in the United States. I recall a pair of “Harper’s Index” statistics in Harper’s Magazine from at least ten years ago:
“Percentage of Americans who believe there is a Heaven in the afterlife: 77
Percentage who believe they will enter therein: 66”
But I wonder what the figures would have been if the surveyor had asked about Americans’ belief in Hell, defined as an afterlife where the damned suffer eternal and unrelenting pain, torment and misery.