The legal term quamdiu se bene gesserit means "as long as he shall behave himself well" (1) and is used when granting an office for an indeterminate time. See this entry in Black's Law Dictionary.

(1) Or she, I might add, not least in light of the fact that in the novel Dune, as noted in this recent question, the "Bene Gesserit" are an exclusively female order.

My question is simple: why is gesserit in the future perfect tense?

I also noticed this is not unheard of in classical Latin either; for example, a common phrase is quamdiu vixero (as long as I shall live), e.g. Socer‚ hoc enim te appellabo, quamdiu vixero (Sen. Controversiae 2,2); this also led to a somewhat inconclusive discussion in this previous question.

But anyway, I can find no justification for the future perfect in connection with quamdiu. What gives?

  • It makes some intuitive sense to me as "if, in retrospect from some future point, he has performed his duties well..." -- though admittedly this kind of interpretation doesn't work as well with the Seneca quote.
    – TKR
    Commented Oct 7, 2021 at 22:54

2 Answers 2


In Gustavus Fischer's Details of Syntax, a number of pages are devoted to the uses of tenses in temporal clauses. It is fairly dense reading, but the most pertinent section is sec. 578, rem. 61. I will quote portions of it below.

Temporal clauses determining the duration of another action by the duration of their own action, answering to the question 'how long,' generally require both predicates to be in the PERFECT. They correspond to English clauses with 'as (so) long as' (or 'while' if it may be replaced by 'as long as'), and are introduced by the conjunctions quamdiu, dum, or quoad.

Some examples Fischer gives:

Hortensius vixit tamdiu quam (or quamdiu) licuit in civitate bene beateque vivere, Hortensius lived as long as it was possible to live honorably and happily in the commonwealth. Cic. Brut. 1.4.

Ego dum vis fuit nihil egi; As long as force was reigning, I did not do anything. Cic. Sest. 60. 127.

Gerd Haverling offers a complementary viewpoint in "Actionality, Tense, and Viewpoint" in New Perspectives on Historical Latin Syntax, vol. 2.

With expressions meaning 'while' or 'for the time that', Latin uses the perfect to give a general overview ... and the imperfect to indicate backgrounding.... The Latin for 'as long as he lived' is dum vixit ..., and the imperfect is only used when backgrounding of the situation is explicitly emphasized.... A similar distribution between the perfect ... and the imperfect ... is found in Latin with quamdiu.

Up to this point, we've seen only past tense uses, but the general idea is that the perfect tense is the default (Fischer) unless the information is specifically intended as background information (Haverling). The situation is somewhat complex in cases of future time.

Haverling notes that in expressions of the sort 'if he lives' and 'as long as he lives', both the simple future and the future perfect are found, even when there is no clear anteriority (what Haverling calls "the absolute-relative sense"). He believes there may be a diachronic component to this:

In the function 'as long as X lives', Early and Classical Latin seems to prefer the simple future ...; when Cicero uses the future perfect of this verb, the absolute-relative sense seems always quite clear.... However, in a passage from the later Classical period and in passages from the first centuries CE, the future perfect appears in expressions meaning 'as long as X lives' ..., just as in Petronius.


Other examples of the development toward a more extensive use of the future perfect are provided by the forms uoluero, which is never used in Early Latin but which is met with in passages from the early first century onward (e.g., Sen. contr. 10,2,1), and potuero, which may easily have been confused with potero in the manuscript tradition, but which nevertheless seems to become common first from the Classical period onward (e.g., (165c) above). There are thus some changes in the use of the future perfect from Early to later Latin, and in certain cases the use of the future perfect becomes more frequent.

The problem in these cases concerns the extent to which the future perfect in some passages refers to absolute-relative time, and to what extent it has to do with an older aspectual system. There seems to be a degree of overlap between the simple future and the future perfect even when the same kind of actionality is expressed, and even in the same verb. There are also some differences between different authors as regards the use of one form or the other. The tendency to use the future perfect in an absolute-relative sense is particularly strong in Classical Latin, but the system is not totally consistent even there. In my view, this indicates that in Early Latin we sometimes have to reckon with some influence from an earlier system in which the absolute-relative function was not yet as clear as it would be in Classical Latin, and that it is likely that some such influence lived on in fixed expressions in the colloquial language even during the Classical and post-Classical periods.

Useful information, to be sure, but no definitive answer as to why a given author chose precisely the construction under consideration. My tentative suggestion is that the perfective aspect of the construction when used in the past may have been felt strongly enough to cause some authors to regard the future perfect as the more natural form.


I only normally come here for Greek, and I don't know any Latin, so the following is just based on looking up information and may be totally wrong.

According to U Chicago's Morpho, there are two possible ways to parse this: perfect subjunctive or future perfect.

Based only on my knowledge of Spanish and Greek, it seems like the subjunctive would make sense because we're expressing a wish or a value judgment, and also something that is in doubt. (It looks like Latin, not being as awesome a language as Greek, doesn't have a separate optative, so they express a wish using a subjunctive.) The future would also make sense, because the patent is being written today and is expressing a condition concerning the person's future behavior.

So the real question is why it's perfect.

If it's future perfect:--

A relevant WP article says, that it's normal to use the future perfect to form "if" clauses about the future. There is no literal "si" or "cum" built into this legal set phrase, but it's clearly expressing a condition. This makes logical sense to me. We have event A in the future which causes event B in the future. By causality, A must precede B in time. Therefore it makes sense to use the perfect for A, because we're implicitly relating it to the later B. In general, Latin seems to use the future perfect in a lot of situations where English would use the present or simple future.

If it's perfect subjunctive: --

The same WP article says, "The perfect subjunctive can also be used in a wish for the future, but this use is described as 'archaic'." This interpretation seems possible but less likely. The legalism would probably not use consciously archaic language, and the phrase doesn't express a wish, value, or command, but something more like an impersonal consequence.

  • 1
    It is true that the phrase I specifically asked about is ambiguous. In the case of vixero we can rule out the subjunctive, though. Commented Oct 8, 2021 at 19:47

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