Accent, ἆρ' ἐστὶ

[Lavrentivs]

Aristotle's Metaphysics 1049 a 1:
οἷον ἡ γῆ ἆρ' ἐστὶ δυνάμει ἄνθρωπος;

Why not ἆρ' ἐστι ?

[anphph]

A circumflex for all purposes means that the accent is on the first time (of two) in the syllable. ἐστι usually takes over the accent of the preceding word, making it for purposes of accentuation one single word — *ἆρεστι — but Greek (unless in very specific circumstances) can only accept an accent in the third times counting from the end, and *ἆρεστι would have it on the fourth. This is unacceptable, and so the last syllable receives an accent. ἆρεστί (which changes graphically to a grave because it precedes a word with an accent).

[calvinist]

A circumflex for all purposes means that the accent is on the first time (of two) in the syllable. ἐστι usually takes over the accent of the preceding word, making it for purposes of accentuation one single word — *ἆρεστι — but Greek (unless in very specific circumstances) can only accept an accent in the third times counting from the end, and *ἆρεστι would have it on the fourth. This is unacceptable, and so the last syllable receives an accent. ἆρεστί (which changes graphically to a grave because it precedes a word with an accent).

Wouldn't ἄνθρωπος violate the rule as you stated it above? The accent is on the fourth mora from the end of the word.

[Paul Derouda]

Wouldn't ἄνθρωπος violate the rule as you stated it above? The accent is on the fourth mora from the end of the word.

But perhaps the accent (i.e. highest pitch) is really on the ν of ἄνθρωπος -- αν being treated as if it were a diphthong?
EDIT: No, I'm just mixing things up and confusing two different things. There's some discussion as to whether the beginning of the Odyssey should be accented ἄνδρά μοι, but that's beside the point.

[anphph]

A circumflex for all purposes means that the accent is on the first time (of two) in the syllable. ἐστι usually takes over the accent of the preceding word, making it for purposes of accentuation one single word — *ἆρεστι — but Greek (unless in very specific circumstances) can only accept an accent in the third times counting from the end, and *ἆρεστι would have it on the fourth. This is unacceptable, and so the last syllable receives an accent. ἆρεστί (which changes graphically to a grave because it precedes a word with an accent).

Wouldn't ἄνθρωπος violate the rule as you stated it above? The accent is on the fourth mora from the end of the word.

Yes of course you are right. I got carried away explaining the logic behind the enclitics; in what we really are counting is the last syllable (the ultima). Smyth #166:

166. When the ultima is long, the acute cannot stand on the antepenult, nor the circumflex on the penult. Thus, ἄνθρωπου and δῶρου are impossible.

[calvinist]

@MiguelM
I think you were trying to find a "unified theory" to explain the rules of Greek accents based on one factor, but it's a combination of syllable position and mora. I think you may be able to explain Latin stress accent merely by mora: "stress the third mora from the end of the word". amáare cápere amaávii

EDIT
Words like famíliaa would violate the ¨third mora from the end¨ rule.