What, if anything, is the elided noun in the phrase a fortiori?
A curious variant and a curious translation
I had been assuming that the full phrase is a fortiori ratione, "with stronger reason", but this answer by @Johann Ramminger just sent me to the following passage from Ockham's Dialogus, part 3, tract 2, book 2, translated here by John Scott, including collations from numerous manuscripts:
Three of the manuscripts have the variant concluditur quod multo fortius…distincta est in place of per consequens a fortiori…. The translator appears to have favored the variant: "It is much more the case that…is distinct." So, the variant and translation seem to take a fortiori to mean that the conclusion is itself stronger, rather than that the conclusion is established with a stronger basis. This suggests that there is actually no elided noun in a fortiori—that the adjective is meant substantively, the phrase perhaps meaning "with greater strength".
Reasoning and evidence?
My first thought is that the above reading is simply a mistake. The reasoning is typical a fortiori: since a king's power does not derive from the pope's, neither can an emperor's, since an emperor's power includes and surpasses that of a king. The subject matter primes such a mistake, since the subject matter is an explicit comparison of (legal) powers.
But I could be wrong. What textual evidence do we have that a fortiori is short for a fortiori ratione—or whatever it's short for, if anything?