The what/which distinction is one I have always been a little hazy about in Latin, so do have patience if the answer to this is too obvious to be worth mentioning.

Doing some work on the more philosophical side of cosmology, there is a distinction to be made:

  1. The whatness of the laws of nature. For instance, "The strength of the force of gravity is X".
  2. The whichness of the laws of nature. For instance, "The strength of the force of gravity could have been X, or Y, or Z, and is in fact X".

I wonder if there are technical terms in philosophical Latin which would distinguish them.

The reason for making this distinction is that a "whatness" question has an answer that is complete in itself - perhaps "137". Asking "Why?" on top of that is not really an expected move in the game, and if the answer is "Because it just is like that", nobody minds very much. On the other hand, a "whichness" answer selects among a number of equally possible values and invites the supplementary question, "Given that they are all equally possible, why is the answer this rather than that?"

It is often helpful to try to translate terms back into Latin or even Greek, to get a handle on how people have been thinking about them before. The languages are often sharper, as well. But in this case, it appears to me that in Latin one deals with quid=what and quid=which by looking at the overall context of the sentence. And certainly quidditas ends up having a basically "whatness" meaning. That is all very well, but it means that one cannot package up the notion of whichness into a simple -itas.

I hope I am missing something very obvious here!

(And Greek being richer in philosophical terms than Latin, a Greek answer would be helpful as well.)

I should add that it is conceivable that "whatness of the laws" might well be better expressed as "what-kind-ness of the universe" - hence, qualitas – but that doesn't help with the whichness question and is, if anything, a step backwards.

  • 3
    Are these your own coined terms? Your example with the laws of nature seems really unnatural to me (and "whichness" has almost no Google results). Aristotle famously divides (in Posterior Analytics B.1) the questions we inquire about into four basic types: "if it is," "what it is," "that it is," "why it is." He later maintains that the first/third and second/fourth collapse together.
    – brianpck
    Oct 20, 2022 at 15:00

1 Answer 1


When asking which of a set, then quis is used with a pronoun in the genitive. For example, quid horum (which of these?) or quis vestrum (which of you?). If there are only two objects then uter can be used.

When asking philosophically about the nature of physical things in general, or a definition for example, then quid is used. So, for example, quid est zingiber? (what is meant by 'zingiber'?). When asking about physical quantities, like the force of gravity, Romans do not generally ask "what is the force of gravity?" they ask "how much is the force of gravity?": quanta est vis gravitatis? If you used quid in this sentence, instead of quanta, the Roman would think you were asking for the definition of the term vis gravitatis.

  • 1
    "When asking philosophically about the nature of physical things in general, or a definition for example, then quid is used with the subjunctive." What makes you say this? Perhaps you're thinking of indirect questions?
    – brianpck
    Oct 20, 2022 at 15:07
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    The Quintilian quote is an indirect question, "[we must define] what is clarigatio...". The indicative is standard in direct questions, see e.g. the many authors listed here, none of whom have to my knowledge been accused of writing the Latin of street slaves: latin.packhum.org/search?q=quid+est
    – TKR
    Oct 20, 2022 at 15:59
  • @tkr alright I will eliminate this element of the answer Oct 20, 2022 at 16:19
  • Thank you for the genitive: it is indeed one of the joys of an inflected language. Oct 21, 2022 at 7:06

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