Let’s look again at the notion of definability, rewritten slightly: for any set A, x⊆A is definable over A if there is a first-order formula φ(y,ū) and elements ā∈A such that Continue reading
Monthly Archives: March 2026
Set Theory Jottings 21. The Constructible Universe
The constructible universe is traditionally denoted L. L is a subclass of V and is a proper class. Gödel proved three things about L: Continue reading
Filed under Set Theory
Diagonal Argument 