Englightenment values would have been familiar to many, but I don't think this would have been a big schism among even the elite at the time, with respect to their own faith.
My guess is that 'rational' could be replaced with 'rigorous'. Or possibly, 'rational' meant to include commonly accepted norms and practices (prayer, attendance) and not a lot of the more hyperbolic stuff that was gaining favor at the time (Spiritualism, the Occult) and other non-doctrine and pagan flavors of practice.
Yes, that is faith in a nutshell. Every attempt to 'reconcile' faith with science, compromises both and does no service to either.
I'm not a person of faith (not in a dogma anyway). But I can understand that to mean anything at all, faith has to mean a different thing than 'observable confirmation of nature'.
Perhaps it is for many, but it isn't for others.
The materialist view inherent in the antagonist's comments isn't necessarily the only rational view.
Materialism, for example, cannot even explain Life, or rather it seems to promote a mechanical basis for it, wherein a more metaphysical view i.e. that 'life is what is expressed through the material, not the material itself' is a pretty obvious opportunity for explenation.
To make the argument: "There is a God" as the basis for Religion, and then "There is only observable material" as the basis for 'Science' is I think wrong on both fronts.
There's quite a lot in between.
My own, personal view is that Spirituality is utterly rational, at least as rational as a materialist who wants to believe that you and I are merely random bags of particles, bouncing through the Universe, and that we're not really having a conversation, that we're two blobs of particles bouncing our 'fingers' of other blobs of particles, in a completely haphazard, random fashion.
I don't even think the Priest was referring to 'rational' in the sense that we might.