Your first sentence is good, except that you need to put "wield" into past tense ("wielded"): "He could have wielded a sword if he hadn’t lost his hands." Your second sentence is grammatically correct, but it doesn't mean quite the same thing as your paraphrase. "I couldn't do that." = "I am not capable of doing that" / "I would not (currently) be able to do that" "I couldn't have done that" = "I didn't have the ability to do that (at the relevant moment in the past)" Peter moved the boulder at a certain time, under certain circumstances. If you want to say that you would not have been able to do the same thing (if you had been there, at the same place and time), you should say "I couldn't have done that." If you want to say that lifting a 200-pound boulder is just, in general, something you don't have the ability to do (at any time), you should say, "I couldn't do that." Your third sentence is good, and matches the paraphrase.