This question originates from the following sentence by Caesar (words in parentheses are omitted in Caesar's original writing),

reī frūmentāriae (Caesarī) prōspiciendum (esse)

in which the compound verb prōspiciō takes dative as its object.

The questions relating to this are:

  1. Why is the dative also used in passive voice as the subject?
  2. Why is the participle prōspiciendum in neutral gender?
  3. If converting rēbus frūmentāriīs plural, what gender and number should prōspiciendum be?

Edit: I read this from Caesar’s Dē Bellō Gallicō A Syntactically Parse Reader by Jean-François R. Mondon, and the main clause of this sentence is

... reī frūmentāriae (Caesarī) prōspiciendum (esse) exīstimāvit

where the omitted words in parentheses are commented by Mondon.

I'd like to make my question clear that it is not quite about the passive periphrastic, but the common passive usage of the verb. For example, the active sentence

Caesar reī frūmentāriae prōspicit.

could be converted into passive voice as (it's just my guess, and may not be correct)

Reī frūmentāriae prōspicitur ā Caesare.

Now what is the subject of this sentence, what is its gender, and what number should it be if rēbus frūmentāriīs is made plural?

  • 2
    How do you know that the missing word is esse rather than est? It helps if you can provide the context that suggests that.
    – Joonas Ilmavirta
    Feb 26 at 9:53

4 Answers 4


What you say in your edit, Maizi Wu, is indeed relevant to clarify your question ("I'd like to make my question clear that it is not quite about the passive periphrastic, but the common passive usage of the verb"). Essentially, the answer to your question (and, in fact, to all your three subquestions) is that both examples Reī frūmentāriae prōspicitur ā Caesare and ... Reī frūmentāriae (sibi: i.e. Caesarī) prōspiciendum (esse) exīstimāvit involve an impersonal construction, i.e. both examples lack a subject.

Your first subquestion ("Why is the dative also used in passive voice as the subject?") wrongly presupposes that these two constructions must have a subject but here we deal with two impersonal constructions, i.e. both lack a subject (NB: the dative complement reī frūmentāriae has the very same syntactic status in the active and passive constructions). Your second subquestion ("Why is the participle prōspiciendum in neutral gender?) has a related answer: it is in neutral gender because the construction is impersonal. Finally, your third subquestion ("If converting rēbus frūmentāriīs plural, what gender and number should prōspiciendum be?") has, again, the same answer: the construction lacks a subject. If you convert the dative complement to plural, the gender and number of the -nd- form remain the same. Why? Because, again, the dative is not the subject.

As you can see, all your three subquestions revolve around the same: the construction is impersonal. So don't expect to find a subject there. Descriptively speaking, there is none!

Once it is clarified that both examples in bold above are impersonal constructions (i.e. they lack a subject), one can wonder if these two examples are equally passive (I know this is not your question, but I can't help saying something more on this related issue as well).

Let's start with the the "easy" case. Descriptively speaking, your (invented but correct) passive construction Reī frūmentāriae prōspicitur ā Caesare lacks a subject, whereby, as noted, it is called impersonal. Impersonal passives are typically made out of agentive intransitive verbs (or agentive transitive verbs that are used intransitively): the so-called "unergative verbs". You can find some hopefully useful discussion of Latin impersonal passives in this link. For the purposes of building an impersonal passive, the issue whether the intransitive verb takes a dative argument or not is mostly irrelevant (NB: as for why I say "mostly" here (rather than "always"), see the brief discussion on the example in (1) below, which is also alluded to in my comment to Joonas's answer).

Now let's deal with the "tricky" case. Don't get suprised if you see that people often concentrate/comment on the passive or active role of the -nd- form of your example from Caesar: ... reī frūmentāriae (sibi: i.e. Caesarī) prōspiciendum (esse) exīstimāvit. This is partly due to an unsolved debate (even in the current specialized literature) about the traditional concept of "passive periphrastic". See this link for a brief discussion.

Here is a synthesis of my personal view:

Impersonal constructions with -nd- forms can be passive (see ex. (1) with an "ablative of agent": est a vobis... consulendum) or not (see ex. (2) with the so-called, in fact, miscalled, "dative of agent": moriendum est omnibus; NB: in this case, the lack of passivization is even more evident because mori is an unaccusative verb: as rightly noted in this wiki link, unaccusative verbs (i.e. those intransitive verbs that are not agentive) do not typically form impersonal passives):

(1) Aguntur bona multorum civium quibus est a vobis et ipsorum causa et rei publicae consulendum. (Cic. Manil. 6) ‘The property of many citizens is at stake, which you ought greatly to regard, both for your own sake, and for that of the republic.’ (C. D. Yonge, 1856, Perseus)

(2) moriendum est enim omnibus (Cic. Tusc. 1, 9, 15) ‘All must indeed die.’

Finally, as for your initial example from Caesar,

(3) rei frumentariae prospiciendum existimavit (Caes. Gal. 1.23)

it would be an excellent question to ask whether prospiciendum (esse) in this particular example is a passive form. Here I tend to agree with Sebastian's comment to Davide's answer and with Joonas's answer: prospiciendum (esse) is an impersonal construction but it is not a passive construction. The basics of my argumentation can be found in this link, which is, indeed, a bit long but, you know, the answer is not an easy one... [NB: Pinkster's (2015) (correct) observation/conclusion in his Oxford Latin Syntax that gerundives are "more frequently active" should not go unnoticed since it goes against what is often found in many traditional grammars of Latin. See also Danesi, Johnson, and Barðdal (2017), who also offer an interesting critique of the traditional claim that a typical gerundive (-nd-) construction with esse is a passive construction. In my opinion, this paper by Danesi et al. is excellent but, unfortunately, they do not take into account the relevance of examples like (1), which contain an ablative of agent. In my opinion, examples like (1) are passive. NB: the typical account that an ablative of agent (a vobis) is used there instead of a "dative of agent" (vobis) to avoid the ambiguity with the other dative (quibus) only offers a partial solution. Similarly, Danesi et al. would also have problems to account for the following examples in (4) and (5), which are clearly passive. In contrast to the example in (1), note that their ablatives of agent (a consulibus & ab oratore) do not seem to be used there because of an ambiguity problem (that's why I said that the typical account of why an ablative of agent is used in (1) is partial):

(4) Sed tamen et Crassus a consulibus meam causam suscipiendam esse dicebat. (Cic. Sest. 41)

(5) Ergo haec et agenda sunt ab oratore, quae explicauit Antonius, et dicenda quodam modo (Cic. De Or. 3, 10, 37).


This is just the gerundive used to signal obligation, and I find it a bit misleading to call it passive periphrasis. Calling the gerundive a passive participle can lead astray.

When there is a direct object, the gerundive takes the gender and number of it. When there is not, the gerundive is in the neuter singular. The latter has happened here, as there is no accusative object. Changing an indirect object to plural has no effect on the gerundive. From the point of view of Latin grammar it is often best to only think of accusative objects as actual and proper objects. Indirect dative objects behave quite differently.

Consider this pair of sentences, one with a mere statement and the other with obligation:

Caesar canit. — Caesar is singing.
Caesari canendum est. — Caesar has to sing.

A similar pair in your case would be:

Caesar rei frumentariae prospicit.
Caesari rei frumentariae prospiciendum est.

Whether you see these as passive at all is a matter of taste. I find it more useful to see this construction as an idiom for obligation. Normal passive sentences (e.g. urbs a Caesare capitur) behave differently from this, and I prefer not to mix the two.

  • I agree. As for your final statement/"preference" ("I prefer not to mix the two"), the thing is that both constructions can be found with such a "mixing": e.g. see my ex. (1), which is a deontic impersonal passive construction: ...quibus est a vobis... consulendum. (Cic. Manil. 6). It is often said that the ablative of agent is used there to avoid the ambiguity with the other dative (quibus) but the thing is that passive gerundi(v)al constructions do exist (typically, in Cicero: e.g. Sed tamen et Crassus a consulibus meam causam suscipiendam esse dicebat. (Cic. Sest. 41)).
    – Mitomino
    Feb 26 at 19:10

The most important concept to grasp is that there isn't really such a thing as a dative "object". Verbs that govern a dative (without an accusative) are intransitive. Thus, they cannot be made passive by transformation. The dative does not indicate the thing being looked at, but rather the intended beneficiary (or at least reference point) of the action "looking off in the distance" or "exercising foresight".

Terence: Ego iam prospiciam mihi (Now I'll look out for myself) The character is not looking out AT himself (me) but generally looking out at circumstances and future opportunities with an eye toward what benefits him.

So then, in your example of Caesar, there is no true passive possible in that sentence. Therefore, the verb is put into the neuter singular gerundive and combined with a form of esse. prospiciendum est means "there must be an exercising of foresight" and the rei frumentariae means the same thing it does in the active: "regarding the grain supply".

Notice that even though the "passive" morphology is used, there is no passive semantically. This is similar to how intransitive verbs borrow the passive morphology to make impersonal statements: ventum est, pugnatur, itur, etc.

  • 1
    I agree. As for your final statement ("even though the "passive" morphology is used, there is no passive semantically. This is similar to..."), I'm not sure if it is clear enough: e.g. note that impersonal passive constructions like pugnatum est do have a passive semantics (unlike the impersonal -nd- example at issue here).
    – Mitomino
    Feb 26 at 18:37

That is a passive periphrastic (gerundive: prospiciendum) used in subordinate clause (accusative + infinitive) that expresses indirect speech. There must be a verb in the main clause indicating the indirect speech.

The passive periphrastic has a meaning of necessity or duty and the person who needs to do it is expressed by the dative (of agent). "We must destroy Carthage" becomes "Carthage must be destroyed by us" and in Latin "Carthago delenda est nobis".

In the example above "delenda" agrees with "Carthago" which is the passive subject. If the passive subject is not specified, the sentence has a more generic meaning and we use the neuter gerundive which is probably the case here.

I am less confident in this but I believe, in this case, it would always be singular as there is no subject expressed (unless) there is in the full sentence (and it would be an accusative because of the subordinate clause).

  • 1
    There is indeed a verb in the main clause "exīstimāvit", but I omitted it since I wanted to focus on "verbs that take dative cases". And thanks for explanations on passive periphrastic, but that kind of deviates from what I inteded to ask. I see in your last paragraph that you mention there is no subject, and this is what I have been confused with. For example, converting the simple sentence "rei frumentariae prospicio" into passive, which I guess could be "rei frumentariae prospicitur a me". So according to your answers, this sentence has no subject, and should be in singular. Is that right?
    – Maizi Wu
    Feb 26 at 7:51
  • 2
    This situation is a good example why calling it the "passive periphrastic" is inadvisable. It would probably clarify matters much more for the OP to say that there is no passive in this sentence. Feb 26 at 8:00

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