 Nevertheless, according to Church, theories that are effectively specifiable (cf. 2.3) can be communicated, inspected, compared with each other and with observational data—as well as evaluated for truth by other rational, checkable procedures. So there is no principled reason (other than Church’s Theorem) why, after rational debate has come to an end, we could not assert the truth of our theory and postulate the existence of its ontological commitments with near certainty. (Of course, in some cases the theory may be underdetermined by the data; and in the case of set theory there may be genuine theory relativity; cf.  §5.4.)