In the lies-to-children/simplification for the purpose of heuristics department there are a largish reference class of these concepts that are basically built into the mind, that there is no way to remotely explain the proper replacement in words due to large amounts of math and technicality and so unknown to almost everyone, but that none the less can be very dangerous to take at face value. Some examples include (with approximate name for replacement concept in parenthesis): "real"(your utility function), "truth"(provability), "free will"(optimizing agent), "is-a"(configuration spaces)