Power was useful but a well studied discipline and proper intent went a long way, too. But there was no real saying how strong Finn would or would not be until he tried.
Luke smiled at that response, because he couldn't help but see a little of himself in it. Although Rey's group was a little more varied, he tended to like them all, and it wasn't impossible to see likenesses in the core trio of Rey, Finn and Poe to Leia, Han and himself. "Seeking knowledge to know yourself and to make your friend proud is hardly a bad reason," he said, even if he was sure Finn didn't think it was a definite one. But it didn't have to be. "I could teach you some, and you could decide if you think it's worth pursuing."