>I know Classical Greek ...
This posting by Richard needs tidying up a little
> consider the parallelism there:
present indicative <-> (nothing)
imperfect <-> aorist indicative
present subjunctive <-> aorist subjunctive
present(?) optative <-> aorist optative
present imperative <-> aorist imperative
These are not parallel. The contrast between continuous ("present") stem
and aorist stem does apply (with some exceptions) to non-finite moods and
forms, but does not apply to to the finite tenses.
>" the Aorist loses the idea of past time"
It is much better to see it the other way round. In some forms it acquires
the idea of past time. It has never had it in the subjunctive, optative,
infinitive etc. and so has not lost it.
>There seems to be a great deal of merit in treating the Greek finite
>forms as being the present, past, subjunctive, optative or imperative
>of the 'continuous', aorist, future and perfect 'aspects'.
Except that some of these forms do not exist. Otherwise this is standard
stuff - but the stems are not parallel.
There are two stems marked for aspect ("present" and aorist), and from these
stems can be formed infinitive, subjunctive, optative, imperative which are
distinguished primarily by the distinction of aspect; but also finite
tenses, where the pattern of contrast is different. No finite tense for
"now" could be formed from the punctative aorist.
There is a further stem marked for resultative state (the "perfect"), with
various formations, all of which retain the concept of state; there is a
yet further stem, a late development within Greek (although built from PIE
elements) which is marekd for future. Some, but not all of the usual forms
can be built from this stem. A fifth stem was developed late as well, to
carry some of the forms which a developing grammar required.
Peter