Frank Kogan

after a quick glance thru critique of pure reason before i went to bed last night, i concluded that
(a) the word "sentence" does not itself appear in the index
(b) the word "ego" appears in the index, immediately redirecting us to the word "self"
(c) the "transcedental self" is indeed distinct from the (normal?) self -- i couldn't find it explicitly defined (though by then i was feeling drowsy) but yes, i take it that it is the constitutive but to us hidden underlying operation which allows our aware self to exist and function as we know it does
(d) hence "to relate" in that extract is not a conscious deliberative act, but a preconscious necessity prior to any possible thought or act

kant doesn't talk about "believing sentences to be true" in so many words -- this i think is back-formation from the later reaches of this history -- but he does for example discuss analytic and synthetic judgments in terms of subjects and predicates (which kept together would always form sentences).

I still have to re-remember kant's particular distinction between concepts and intutions before i can master the last section of that quote, however -- bright morning and strong coffee not yet enough!
(my suspicion is that there's a terminological anachronism here which rorty would justify by noting that he is describing the continuous history of an error: since the neo-kantians argued X, and derived it from kant, then kant must also to all intents and purposes have believed X, albeit in different types of phrasing)