I’ve read the Catechism before, but that doesn’t stop things from leaping out at me when I’m going through it.
Today something leapt out that deals with the problem of evil, even though it wasn’t in the section on the problem of evil. It deals with the question of why God allowed original sin to take place.
Here’s what it says:
412 But why did God not prevent the first man from sinning? St. Leo the Great responds, “Christ’s inexpressible grace gave us blessings better than those the demon’s envy had taken away.” and St. Thomas Aquinas wrote, “There is nothing to prevent human nature’s being raised up to something greater, even after sin; God permits evil in order to draw forth some greater good. Thus St. Paul says, ‘Where sin increased, grace abounded all the more’; and the Exsultet sings, ‘O happy fault,. . . which gained for us so great a Redeemer!'”
The answers provided by Leo the Great, Aquinas, Paul, and the Exsultet all converge on the idea that God allowed man to fall into sin because he knew he could bring about a greater good by doing so.
This does not necessarily mean a greater good for every individual (e.g., people who commit mortal sin and decide to stay there may not end up with a greater benefit in the long run, although this is itself arguable), but it does mean that there will be greater net good in general.