Testing what theory we control for.

It seems I might be overlooking something in the PCT-MCT discussion (which
I also might be overlooking in the PCT-Behavioral discussion). Suppose
that I suspected someone to be controlling for PCT. How might I use the
test to confirm/disconfirm my suspicion? Suppose I suspected someone to
be controlling for some alternative set of principles to PCT. How might
I confirm/disconfirm my suspicion?

It seems that if I were controlling for PCT, then I would resist any/all
attempts to persuade me otherwise. Likewise, in the event I were
controlling for NOT-PCT, then i might just resist any/all attempts to
enlighten me otherwise. In either case, how do I know what theory
someone else might be controlling for, and then how do I conduct a
conversation which either helps them see the error of their ways, or come
more judiciously to my own enlightment/epiphany? Any thoughts?

Thanks, Greg Wierzbicki