I'm afraid you sort of lost me after "mental concepts", so the followong might not apply, but: "deepest principles" make no sense in an appropriate (as worked out by schaffer in the paper) account of infinite levels. His idea is that since every level is grounded by AND grounds another level, all entities on all levels are on an equal footing, including mental entities.
I suspected you might pay attention to that detail. The appropriate generalization just says that you don't expect the same laws to apply at different levels (between levels): a concept in a mind (in a brain, that is a system constructed on top/in terms of lower levels) won't obey the same laws as the lower-level stuff from which the mind is built. There is also a nice antisymmetry here: a mind can look at lower levels and organize its thoughts to model them, but lower levels can't do the same to the thoughts in a mind.
(Last month's started a little late, I thought I'd bring it back to its original schedule.)
A monthly thread for posting any interesting rationality-related quotes you've seen recently on the Internet, or had stored in your quotesfile for ages.