>>11686008no. subset of all subsets is of type "set of sets". if it were to contain itself as a subset, then it would be of type "set of sets of sets"
X = {a, b, c}
P(X) = {{}, {a}, {b}, {c}, {a, b}, {a, c}, {b, c}, {a, b, c}}
P(X) not in P(X)
if you don't define your universe, you will likely end up with paradoxes and contradictions when trying to self-reference
>>11686665membership is the foundational set relation. you can't talk about sets if you don't have a concept of membership
