In Michael Sipser’s Introduction to the Theory of Computation textbook, he has one Platonically perfect homework exercise, so perfect that I can reconstruct it from memory despite not having opened the book for over a decade. It goes like this: Let f:{0,1}*→{0,1} be the constant 1 function if God exists, or the constant 0 function if God does not exist. Is f computable? (Hint: The answer does not depend on your religious beliefs.) The correct answer is that yes, f is computable. Why? Because ...