Can anyone explain why the perfect tense of the potential subjunctive is translated with the present tense (e.g. crediderim is “I would believe,” not “I would have believed”). Clearly this is the correct translation; I am just wondering what the rationale behind it is.
That’s an interesting question, and one that I’ve never given much thought to. But one thing that I think must be relevant is the notorious poverty of linguistic expression available to Latin, unlike Greek or English. No optative, no ἄν, no “would,” only the subjunctive itself, and the past tenses of the subjunctive (imperfect and pluperfect) already taken, commandeered for contrafactuals corresponding to imperf.indic.+ἄν and aor.indic.+ἄν in Greek.
As for the difference between crediderim and credam, I wonder whether in fact that was in origin aspectual, like the aorist/present tense distinction in Greek. As you point out, it doesn’t appear to be temporal. And if the crediderim construction is not pre-Ciceronian, it may even have been a self-conscious innovation.
Thanks, an aspectual origin would make sense (and I can’t think of any alternative explanations).