Set Theory with a Universal Set: Exploring an Untyped Universe

Set theory is concerned with the foundations of mathematics. In the original formulations, there were paradoxes concerning the idea of the "set of all sets." Current standard theory (Zermelo-Fraenkel) avoids these paradoxes by restricting the way sets may be formed by other sets specifically to disallow the possibility of forming the set of all sets. In the 1930s, Quine proposed a different form of set theory in which the set of all sets— the universal set— is allowed, but other restrictions …