mistakes being sufficient to justify punishment for being required to
Why this is right
If we're familiar with our Famous Flaws (and especially the #1 most common / most important one), then we'll instantly see this answer as we scan for the words Necessary vs. Sufficient. If we're trying to figure out this language on the fly, the word "if" in the first sentence introduces a sufficient condition. If punishment actually then, punishment deters people from for crimes is justified committing crimes All the author needs to know is that the punishment deters people and he thinks that is enough (that is sufficient) to show that it's justified. When he starts acting like, "if it's not deterring, then it's never justified" he was switched to treating deterrence as the only (a required) way to justify punishment. It would be the same as if I went from saying, "Law school admissions will be impressed if you have a letter of recommendation from a famous judge who knows you. But Emily doesn't know any famous judges. So Emily will never be able to impress a law school admissions board." Whoa-whoa-whoa ... who said you need a letter of rec from RBG (RIP) to impress? Maybe you're a Rhodes Scholar or have performed at the Kennedy Center. When we go from saying "if it's true, you're good to go" to saying "if it's not there, you're screwed" we've gone from acting like something is Sufficient to acting like it's Necessary.
Skill tested: Flaw · how this choice captures the argument's function is the move to repeat next time.