[Footnote 5: The Missi of Charlemagne pressed him to
declare, that all who rejected the filioque, or at least the
doctrine, must be damned. All, replies the pope, are not
capable of reaching the altiora mysteria qui potuerit, et
non voluerit, salvus esse non potest, (Collect. Concil. tom.
ix. p. 277 - 286.) The potuerit would leave a large loophole
of salvation!]