2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/111497We survey the use of extra-set-theoretic hypotheses, mainly the continuum hypothesis, in the C*-algebra literature. The Calkin algebra emerges as a basic object of interest.16 pages; to appear in Bull. Symb. LogicLogicFunctional AnalysisOperator Algebras03E35; 03E50; 03E75; 46L05; 46L85text