Subjunctive.
The Latin Subjunctive combines the functions of the Greek
Subjunctive and Optative. Comparative Philology tells us that
forms in
-im were originally Optative-forms; thus
sim, older
siēm,
is the Latin equivalent of Gk.
ἐσίην, εἴην while the Latin Future
ero
(from
eso) is the equivalent of the Gk. Subjunctive
ὦ, older
ἔσω. Old Latin
forms like
amassim, prohibessim, faxim were apparently originally
S-Aorist Optatives, and in the language of Plautus' time they still
retain traces of their origin; for in 3rd Person they are in independent
sentences mainly used in prayers and curses, e.g.
di melius faxint
(passim), “
Iuppiter prohibessit”
Pseud. 14; in 1st Person they are appropriate
to Conditional statements, e.g. “
haud (non) ausim”
Aul. 474, etc.;
in 2nd Person to Prohibitions, e.g. “
ne dixis”
Asin. 839, etc.,
“
cave respexis”
Most. 523. (For a full account of these
-sim forms in independent
sentences in Plautus, see Morris in Amer. Journ. Phil. 18, 165 sqq.)