English has expresses advice in the present and past through the use of the following modal constructions:

  • present: You should [...]
  • present negated: You shouldn't [...]
  • past: You should have [...]
  • past negated: You shouldn't have [...]

I am somewhat unsure about how to express either of these in Latin. My gut feeling for expressing the present modalities is to simply use the present subjunctive, e.g:

rogēs eum ut faciat prō tē illud -- you should ask him to do that for you
nōn trānseās illud flūmen, mī amīce -- you should not cross that river, my friend

However, when it comes to expressing the past modality, I am lost. I am not even sure if the other three subjunctive tenses would work to express this.

How would one go about expressing the modalities of advice, listed above, in Latin?

  • 2
    Besides debeo, there is oportet, with various infinitives; and licet similarly.
    – Hugh
    Oct 13, 2018 at 21:49

1 Answer 1


One way you can do this is using the verb debeo, debere, debui, debitus, which not only means "to owe," but also "ought/should." It's relatively simple in its construction, so lets go through each scenario you gave using the verb amo for the thing you should be doing.

You should love him

So first, one puts debeo into the second person singular. Then, one attaches the infinitive and adds the object of the infinitive.

Debes amare eum = "You ought to love him."

Likewise, for the negative, one adds non to this construction.

Debes non amare eum = "You ought not to love him."

For expressing advice in the past, use the perfect infinitive rather than the present.

Debes amavisse eum = "You ought to have loved him."

Debes non amavisse eum = "You ought not to have loved him."

In summary, debeo can be used to express advice as given. There may be other ways to express these ideas, but this is the first of which I thought.

Specifically, the examples you gave would be translated as follows using this method:

Debes rogare eum ut faciat pro te illud

Debes non transire illud flumen, mi amice

As pointed out by cnread, the non and the time were most likely reflected in debeo, and not the infinitive as I stated. To adjust the last example where both are used:

Non debuisti amare eum

  • Ēheu! Don't know how this managed to slip my mind. Grātiās tibi! Oct 12, 2018 at 19:03
  • 3
    Actually, in 'unmarked' (unemphatic) usage, I think negation and indications of tense tend to be shown on the modal, not the infinitive; so non debes eum amare instead of debes eum non amare, debuisti eum amare instead of debes eum amavisse, non debuisti eum amare instead of debes eum non amavisse, etc. Indeed, Gildersleeve & Lodge 280.2.b discusses the tense issue. Allen & Greenough discusses it in 486.a and .b, noting that the present tense of debeo with perfect infinitive is used for special emphasis.
    – cnread
    Oct 12, 2018 at 20:00
  • @cnread Thanks for pointing this out, I'll make an edit to reflect your comment
    – Sam K
    Oct 12, 2018 at 20:30

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