hi, this topic has always interested me and i once wrote an essay on this phrase during my philosophy degree, but over a decade later and with more reading of aristotle, my thoughts on the meaning have changed.
i used to be quite convinced that the imperfect meant what others above had said, that it refers to identity/unity through time.
i spent a lot of time at that time reading the metaphysics, and i haven't read it closely for years and so my current thoughts may be worse than before rather than a positive development.
but i now wonder whether the imperfect was chosen for some syntactic reason in the articular infinitive that i don't fully understand than for a semantic reason (i.e. to show unity through time), because:
- in my quick searches the imperfect only seems to be used in the articular infinitive, and outside that construction there are many references to "τὸ τί ἐστι" etc. where the imperfect doesn't appear
- in aristotle's texts diachronic unity isn't to my memory singled out as the key property of this concept, things like being able to accept contraries etc. come more quickly to mind
there is an allure about finding in the imperfect the meaning of the whole expression, but when i take a step back i remember that trying to understand a concept through its etymology/breaking down its elements is often deceptive (e.g. someone trying to understand what "sweetmeats" in english means may be misled if they started from a breakdown of the elements of the word, and then would be baffled if they read elsewhere that sweetmeats are appropriate for vegetarians...)
and so similarly for this phrase, if i had time to pick up this analysis again, i would instead focus more on exactly how it is used in the metaphysics (its frequent coupling with ἡ οὐσία, how it figures in the τὸ ὑποκείμενον in 1013b, how it is expressed by ὁ λόγος in 983a, etc) rather than focusing on the elements of the word itself. we simply don't know whether aristotle built this word himself to express something critical about the concept, or took it over from someone else at the academy or elsewhere, or built it but on analogy from another concept where the imperfect made sense and where aristotle retained the construction, etc.
i haven't had a chance to investigate any of the above but thought i'd tack my unfinished thoughts on to the end of the discussion, to ask this one question: has anyone been looking at the commentaries on this and seen whether anyone speculates that the imperfect may have been used for syntactic rather than semantic reasons? thanks! cheers, chad