Before we understand the gerundive of a deponent verb, we need to first understand the particples of deponent verbs.
Participles of Deponent Verbs
Deponent verbs are often described as verbs with "passive forms but active meanings." While this generally holds true, it ignores a crucial extra step: deponents have participles in both voices! (See Allen & Greenborough, ch. 190)
For example, patior:
- Present Active: patiens, "suffering"
- Future Active: passurus, "about to suffer"
- Perfect Passive: passus, "having suffered"
- Future Passive: patiendus, "to be suffered"
Note that there are some perfect passive participles that have a passive meaning. Allen & Greenborough give the examples of mercatus ("bought") and adeptus ("gained," though it also can be active: "having gained").
Gerundive of Deponent Verbs
The gerundive of deponent verbs is passive in form and in meaning. The gerundive of obligation is thus used the same as its active counterparts. Allen & Greenborough (op. cit.) says:
d. The gerundive, being passive in meaning, is found only in transitive verbs, or intransitive verbs used impersonally:—
hōc cōnfitendum est, this must be acknowledged.
moriendum est omnibus, all must die.
The ambiguity arises, though, when we consider that the last impersonal construction can be used for all gerundives, deponent or not, to signify an obligation with an "active" meaning.
This is the same problem as with non-deponent verbs. Cicero offers a great example that uses the gerundive in both ways:
Sentio, iudices, moderandum mihi esse iam orationi meae fugiendamque vestram satietatem. (Cicero, In Verrem 2.3.103)
Judges, I sense that **I should limit my speech [in length] and that your satiety [with my speaking] should be avoided.
Note how the gerundive of moderor is used impersonally of mihi to indicate an "active" obligation: "I must moderate" where as the gerundive of fugio agrees with a noun for a "passive" obligation: "X must be avoided". This is merely a difference in translation, though, and the underlying construction is the same.
Thus, if I want to say "X must be endured," I can freely use "X" as the subject of the sentence: "Hoc patiendum est." Enter Cicero:
Ideo fortiter omne patiendum est quia non, ut putamus, incidunt cuncta sed ueniunt. (Seneca iunior, Dialogi 126.96.36.199)
If I want to say "X must endure Y," I have to rearrange so that Y is the subject and X is in the dative: "Hoc patiendum est mihi." Enter Seneca:
Dicentur tibi ista, si operae pretium habebit perseverantia, si nihil indignum bono viro faciendum patiendumve erit; alioqui sordido se et contumelioso labore non conteret nec in negotiis erit negotii causa. (Seneca iunior, Epistulae Morales ad Lucilium 22.8)
There is no case where "Hoc patiendum est" can be construed as "This should suffer."