Recent content by omega

Rigor and intuition are both important in math. Try the books How to Prove It and How to Solve It

You are right, I should have said it is a "commutative diagram" of models. Hamkins considers ill-founded models, which I guess is not super popular, plus he considers not just "M is a transitive subclass of N" but all kinds of embeddings, like those coming from ultrapowers, so it is indeed more...

Let ##(M_i)_{i\in I}## be a multiverse of models of ZFC. By that I mean: Each ##M_i## is a well-founded model of ZFC. ##(I,\leq_I)## is a partially ordered set, and whenever ##i\leq_I j##, there is an embedding ##\tau^j_i:M_i\rightarrow M_j## such that the image of ##M_i## is a transitive...