 While Church may have wished to postulate an absolute realm of sets, just as he postulated such a realm of senses, in neither case was he happy to affirm the existence of such entities without first formulating an axiomatic theory of them and then evaluating it for truth (see  section 6).  The independence from the axioms of ZFC of a natural set-theoretic question like that of the cardinality of the continuum showed that Church’s strictures could not be met without the discovery of another axiom. Absent this discovery, Church hesitated to postulate an absolute realm of sets and even noted the possibility of set-theoretic relativism: that there could be “rival set theories” and that sets “have their reality only relative to and within a certain theory” (1966 [BE: 677]).