When verbs that recommend an action to some degree (such as should, must, ought) are negated, there are two possible interpretations: (a) the action is simply not recommended, nor anything else; or (b) it is recommended to desist from the action. In English, it depends on the verb which interpretation is correct, but for each verb it is generally unambiguous.

For example:

  • you should go → recommendation; you should not go → recommendation to stay
  • you need to go → requirement; you need not go → simple absence of requirement, but go if you want

Some expressions are ambiguous and the meaning depends on context, possibly even on intonation.

All this raises the question how Latin's own oportere reacts to negation. In short, what does this sentence mean?

Te ire non oportet.

  • You must not go?
  • You need not go?

It is not self-evident, is it? To my surprise, the dictionaries I usually rely on are by and large not helpful. For example, Lewis & Short do not explicitly say how it works, and they give a few negated examples, but without translation.

I think of the core meaning of oportet as being along the lines of “it is proper,” with the negation meaning “it is improper” (there being, in my mind, no middle ground). So it expresses a more or less strong recommendation to desist from the action, and the sentence above means “It is not proper that you go; you must not, ought not go” or something to that effect.

But maybe I am wrong. I was made aware of this problem by a recent question asking for a Latin phrase for “it goes without saying.” A (since-deleted) answer suggested a phrase based on a quote by Thomas Aquinas, who said (Summa Theologiae 1, Q 52):

Et secundum hoc patet quod non oportet dicere quod Angelus commensuretur loco.

And sure enough, there is a translation that claims this means “there is no need for saying …” – I think this makes little sense in context, but then again this translation is actually officially sanctioned by the Catholic church.

  • Regarding the last point: an imprimatur or nihil obstat isn't a guarantee that there aren't translation errors. I do a lot of work in medieval philosophy, and this particular translation is well known for often being inaccurate.
    – brianpck
    Commented Apr 28, 2020 at 18:14
  • 1
    I think I remember learning oportet as 'it behoves.' That would support +'need;' but it's not real evidence.
    – Hugh
    Commented Apr 29, 2020 at 1:36

2 Answers 2


It means you shouldn't do it.

My four favorite Latin dictionaries, Lewis and Short, Traupman, Chambers-Murray, and Stelton all let me down on the meaning of non oportet, but I finally found an answer in Woodcock's New Latin Syntax, Number 123. He cites Non te oportebat illi argentum reddere (you ought not to have paid him the money) and, in Livy 5,4,9, non suscipi bellum oportuit (the war should not have been undertaken).

  • 1
    Very nice to have an “official” statement of sorts, but still it is strange that the usual suspects do not come right out and say explicitly how to interpret this. Another example that drives home the “it is proper/improper” aspect is Cic. Pro Flacco, 86. Commented May 1, 2020 at 18:58
  • @SebastianKoppehel I agree that it is mysterious and annoying that non of my dictionaries tell me what non oportet means.
    – Figulus
    Commented May 2, 2020 at 19:47

One more passage apparently favoring the “should not” meaning: Cicero, De Finibus 2.104, refers to a saying that “good memories do not fade for the wise man; bad memories he should not (non oportere) remember.” It seems superfluous to use the wise man standard for something that is unnecessary rather than improper.

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