Is there a common phrase to say "everyone knows x"? I always thought it would be "x is vox populi", but the way I understand from Wikipedia is that vox populi has an opinion content to it.
There are many constructions that might be appropriate.
- certum est (with accusative and infinitive) -- it is certain
- constat inter omnes (with accusative and infinitive) -- it is agreed upon by everyone
- omnibus patet (with subject) -- [x] is plain to everyone
- omnibus lucet (with subject) -- [x] is clear to everyone
More rhetorical options:
- Quis est qui neget? -- who is there who would deny [x]? i.e., everybody agrees on [x]
- Quis est qui nesciat? -- who is there who doesn't know [x]? i.e., everybody knows [x]
- Nemo est tam stultus qui non intellegat -- there is nobody so stupid as to not understand [x]
Vox populi literally means "the voice of the people," so it does indeed not seem very appropriate.
In Latin, a common expression for "everybody knows" is omnibus notum est, e.g. Omnibus notum est Sergium virum sapientissimum esse = "Everbody knows that Sergius is a very wise man"; or: Sergius ceteros sapientia praestat, ut omnibus notum est = "Sergius surpasses the others in wisdom, as everybody knows." You can also make the generally-known thing the subject, e.g. Sapientia Sergii omnibus nota est (note gender) = "Sergius' wisdom is known to all." In medieval legal documents you will also sometimes read Notum sit omnibus (let everybody know), usually followed by a quod clause, a typical feature of medieval Latin.
How to use this in English?
You could perhaps say: "X is an omnibus notum." But that is not an established expression. I'm not aware of an established English expression -- Latinate or not -- for this idea.
One option is certum est ... literally: it is certain/fixed/established. Though it can be somewhat wider in meaning and/or pertain to the individual rather than general knowledge (especially when attached with a dative).
Usually it comes with acc+inf stracture. or with quod
certum est [canes] iuxta Nilum amnem currentes lambere, ne crocodilorum aviditati occasionem praebeant (Pliny the Elder, Naturalis Historia, 8.149) [It is known that the dogs by the Nile lap up water from the river as they run, so as not to give the greed of the crocodiles its chance (Loeb translation)].
A fun possibility is "lippis et tonsoribus" (Horace, Sat. 1.7.1-3), which literally means "to the bleary-eyed and to the barbers" and figuratively means "to everyone". It is mainly used to talk about something which is known to everyone.
The interpretation of the second term is quite obvious, barbers still being a gossip center in many cultures. The first term is of more difficult interpretation: possibly bleary-eyed people in Rome had to apply a particular ointment and to stay still for some time, giving them time to gossip.
This is for sure not a common phrase, but I thought it might be interesting...
My latin isn't (nearly) good enough to lay this out more directly myself, but I had previously understood that "everyone knows" is usually written most idiomatically as
(which dictionary translates fairly literally as "everyone knows")
It's possible, however, that this is a specific turn of phrase used more in legal related wording such as around the concept of notorium, since that's where I've mostly seen it personally.
Notorium est, quod omnes sciunt
is translated by the German wikipedia page for the legal word of art "Notoriety" as, roughly (aka using Google translate from „notorisch ist eine Tatsache, die allen bekannt ist“), "notorious is a fact known to all".
And from Bartolus' In ius universum civile commentaria, Dig. 11.7.4 no. 2, when discussing the concept of notorium:
Sed quid arbitrabitur iudex? Dicas quod verum notorium est quando factum est tale de sua natura quod omnes sciunt vel scire eos verisimile sit, sic quod non possit allegare ignorantiam, quin sit supina, sicut si quis gerat se pro episcopo in aliqua civitate, vel si quis in veritate toto populo aspiciente occidit hominem.
Which "Conviction According to Conscience: The Medieval Jurists' Debate Concerning Judicial Discretion and the Law of Proof" (full article is paywalled or requires institutional access) explains with
Bartolus asked, "What is there for a judge to determine?" The only fact that is genuinely notorious is one that, by its very nature, everybody knows or ought to know, so that one cannot claim to be ignorant of it without admitting that one's ignorance amounts to negligence.