It's a bit of a startling thought, for Lucius - a world with no muggles at all, or no true muggles as he knows them.

"In our world, there's no potential. One is either a wizard or witch, or one isn't." He doesn't go into things like squibs; the principle still holds. "One can receive a variety of training, but in all but the most extreme situations, I could no more stop being a wizard than stop breathing. And I would have about as much desire to." Potential was only applicable to young children, and even then some manifested early enough it was clear.

"But if it's long enough ago for it to be a myth, you must be used to it, your way."