(see J. Heckmann in Indogermanische Forschungen,
18, pp. 296 sqq.).
Comparative Philology has corrected the old notion that -ī was
in all Declensions the Locative suffix (e.g. Romai, Corinthi, Carthagini
and has shown that in Ā-stems (1 Declension) the suffix was -ai, a diphthong
(while the Genitive suffix was disyllabic -āī), in O-stems (2
Declension) -oi (cf. Gk. οἴκοι
) which became -ei, and later (after Plautus'
time) -ī, in Consonant-stems (part of 3 Declension) -ĭ, which became -ĕ.
This Consonant-stem Locative was used in Latin as Ablative, e.g. Carthaginĕ,
in Greek as Dative, e.g. πατρί.
Instead of this Ablative-Locative -ĕ
in Consonant-stems we find occasionally -ī in Plautus, e.g. militi,
seems to be the I-stem Ablative (originally -īd), e.g. navī, classī.
as the Consonant-stem suffix -ĕ was often used in I-stems, e.g. navĕ,
and (in Plautus) marĕ,
so the I-stem suffix -ī(d) found its
way into Consonant-stems. If this be the true explanation, Carthagini,
etc., and in Plautus Accherunti
‘in the lower world,’ e.g.
, are Ablatives, not Locatives.