“You’ve built your #theorem on a foundation of false assumptions,” said the demon, taking the chalk away. “Two plus two is no more four than it is blue or apple. The pipe is not a pipe, except when it is.” He corrected runes and swapped out the incense. “Come, try again.”

“If you wanted junk science, you should’ve picked the theology wing,” grumbled the grad student. “I’m still not sure you exist.”

Together they rebuilt apples into oranges until the banishing circle was complete.

“Theorem proved,” the demon said happily, and vanished.