"Oh, that is simple," and while he can imagine being soundly mocked by Warthrop for accepting this answer, he also has the skeleton as proof right before his eyes. Maybe magic itself isn't as simple as the skeleton makes it sound though, that much at least seems logical. "If biology doesn't matter, what do people study and learn about?"

He's the apprentice of a full-time, professional scientist. His world is dominated by the rigors of science. All the papers to be read, all the correspondence to be kept, all the specimens to collect, and dissections to conduct. He's trying to imagine a world where that is now optional, a world where the rules could just be thrown out--

It is, definitely, existentially disturbing but maybe Will Henry is still child enough he can imagine some giddy relief in it all.