Is Russell's Paradox a semantic paradox or a syntactic paradox? I ask because of the following:
Let P be a predicate
Let SEP be the property of being a set of things that satisfies P
Let SP be the property of satisfying P
Let NA be the property of not being in A
∃A∃B(SEP(A)∧SP(B)∧NA(B))→∀A∃B(SEP(A)→SP(B)∧NA(B))
(5) is true since it is a validity in first order logic. Also, the antecedent is true. Thus, the consequent is true too.
∀A∃B(SEP(A)→SP(B)∧NA(B))≡∀A(SEP(A)→∃SP(B)∧NA(B))
∀A(SEP(A)→∃B(SP(B)∧NA(B)))≡∀A(¬∃B(SP(B)∧NA(B))→¬SEP(A))
∀A(¬∃B(SP(B)∧NA(B))→¬SEP(A)) translates to: For all A, if there doesn’t exist B such that B has the property of satisfying P and B has the property of not being in A, then A doesn’t have the property of being a set of things that satisfy P.
(9) is relevant because of the following: Let P be the predicate not a member of itself. So, we have: For all A, if there doesn’t exist B such that it has the property of not being a member of itself and the property of not being in A, then A doesn’t have the property of being a set of things that aren’t members of themselves.