Real-world – generated sets are such that one is only rarely a proper subset of another, because each has at least one wisp, or tail (like a solar flare) that grows with time. (Corollary: Perfect order (and perfect disorder) is not possible. Hence, Gödel’s Theorem is also a corollary.) A reliable procedure for un-doing tails of a given type is called an algorithm. If a given (‘bad’) set needs to be destroyed, it may be easier to destroy a superset of it (cf: extraneous roots), but if you wait too long, the tail of the bad set will be so long that the smallest convenient superset of it is so large that destroying that superset would waste considerable resources. It is in such cases that an algorithm is called for.