Implicature of "Deem"

Referred yet again by Grice, PPQ, vol. 67, p. 31 -- cfr. "Meaning Revisited" in WoW.

"A certain Oxford college was once
embarrassed by a situation in which its
newly elected Provost wished to house
in his lodgings his old and dearly
beloved dog, but in the way of this
natural step stood a college statute
forbidding the keeping of dogs within the
college. The governing body ingeniously
solved this problem by passing a
resolution deeming the provost's dog
a cat."

"It may be said [wrongly] that"

"it could ONLY be deemed [emphasis Grice's]
a cat if it were in fact not a cat."

---- Grice uses this implicature to note that Davidson ignores it. "So with actions and action-surrogates." Yet, because Davidson unpreparedly goes to ontologise action-talk without the proper 'linguistic botany' that we find attracted to repel Davidson's theory!