An Sit versus Quid Est

[Cheiromancer]

This is a Greek/Latin question, so I've also posted in the Greek forum. It's from Quintilian's Institutes on Oratory (III, 6, 23-24).

Ac primum Aristoteles elementa decem constituit, circa quae versari videatur omnis quaestio: οὐσία,quam Plautus essentiam vocat (neque sane aliud est eius nomen Latinum), sed ea quaeritur "an sit".

Now I thought that the first category of Aristotle, the τί ἐστι, was "what" something was, not "whether" it was. Quintilian is using the alternative name for the first category, οὐσία, but seems to be construing the category as "whether" a thing is instead of "what" a thing is. I would have thought that instead of "an sit" he should have written "quid est".

Any thoughts?

[adrianus]

I imagine it appropriate ("an sit") as a question relating to what distinguishes corporal from incorporal things and imaginings. Essence as a category would address this (whether something exists corporeally), but asking what something is doesn't. More to the point, however, is this. The Latin word essentia derives from the verb of being (the verb 'to be'); hence the question "an sit". All the categories address what things are but in different ways. An sit emphasizes the verb esse as central to the derivation of the Latin word essentia; quid est emphasizes the word quid and not the verb esse.

Ita significatur, id mihi videtur: an corporalis sit quaedam res, id est per materiâ exstet, an non exstet separatim in mente seu incorporaliter. De hâc essentia tractat. Melius autem sequente in modo cogitare. Quod essentia ex esse verbo derivata est, apta est talia quaestio distinguens, an res sit.

Post scriptum
Conjunctionem scilicet sed modo animadverti. Mordeatne Quintilianus electionem essentiae verbi Flavio factam quod illud nomen magis verbum esse spectat, non materiam rei? Certùm, ita nunc mihi videtur. Verè quod dicis Quintilianus dicit de nomine Latino essentiae vel de derivatione eiusdem.
I just noticed the word "but". Could it be Quintilian is criticizing the Latin word essentia of Plautus/Flavius because it focusses on the whetherness of being versus non being? Indeed, I think that's what he is doing. Quintilanus is actually saying what you are saying but about the Latin word essentia or its derivation.