9 kinds of hard-to-verify tasks

Introduction Some people talk about "hard-to-verify tasks" and "easy-to-verify tasks" like these are both natural kinds. But I think splitting tasks into "easy-to-verify" and "hard-to-verify" is like splitting birds into ravens and non-ravens. Easy-to-verify tasks are easy for the same reason — there's a known short program that takes a task specification and a candidate solution, and outputs a score, without using substantial resources or causing undesirable side effects. By contrast, "hard-to-verify tasks" is a negative category — it just means no such program exists...