Wizardry Violates the Conservation of Energy

“You turned into a cat! A small cat! You violated Conservation of Energy! That’s not just an arbitrary rule, it’s implied by the form of the quantum Hamiltonian! Rejecting it destroys unitarity and then you get ftl signaling! And cats are complicated! A human mind can’t just visualize a whole cat’s anatomy and, and all the cat biochemistry, and what about the neurology? How can you go on thinking using a catsized brain?” McGonagall’s lips were twitching harder now. “Magic.”...

 Metaphor for the Spread of Disease

To choose a rough example, think of a thorn which has stuck in a finger and produces an inflammation and suppuration. Should the thorn be discharged with the pus, then the finger of another individual may be pricked with it, and the disease may be produced a second time. In this case it would not be the disease, not even its product, that would be transmitted by the thorn, but rather the stimulus which engendered it. Now supposing that the thorn is capable of multiplying in the sick body, or ...