> The form /e:st/ "he / she eats" seems to be a contraction of a more
> regular /edit/,
Actually of ed-t athematic, with sound changes.
>I'm rather doubtful about vowel length, which was
> not marked in close syllables
Vowel length in closed syllables can in general be established in other
ways, e.g. by comments from Latin grammarians, or from the Romance reflexes.
But unfortunately in this word, the evidence is scanty. What there is,
though, is not disputed, and the athematic forms of the word are always
given as from the stem e:s with long e:
e:sse to eat vs esse to be
e:sti (you plural eat) vs esti (you plural are)
The vowel length can be seen in the 2nd singular e:s (vs es you are), and
in the particple e:sus and come:stus (eaten up).
The only exception is the athematic subjunctive edim, edis etc, with
short e.
Thematic forms of the stem also have short e, as edo, edimus, edunt.
This pattern suggests strongly that we have a sound change:
*ed + vowel > ed-
*ed + dental consonant > e:s-
but the details are disputed.
Peter