“…Good examples here are so called large cardinal axioms, as well as forcing axioms, and inner model hypotheses.10 Here we are playing slightly fast-and-loose with debates in the foundations of set theory; under a natural interpretation of Joel Hamkins' multiverse perspective, set theory also should be understood as purely algebraic. See[Hamkins, 2012] for the original presentation of this view and[Barton, 2016] for an argument to the effect that this results in a purely algebraic interpretation.11 The exact dialectic import of a categoricity proof is something of a vexed question, see[Meadows, 2013] for discussion. An argument that the quasi-categoricity of ZFC 2 shows that our axiomatisation has been successful is available in[Isaacson, 2011].12 The original proof of this is available in[Zermelo, 1930], and is subsequently tidied up in[Shepherdson, 1951] and[Shepherdson, 1952].…”