My effort:
And pardon [is allowable to us], as not with any evil purpose we undertake the opposite of our earlier isolation, which was a error of judgment.
My effort is a collage of guesses. I request an explanation of the Greek grammar of this sentence, showing how the words fit in it.
Collage of guesses or not, Hugh, you appear to have mostly recognized how the words fit together. The sentence does not quite say what it means. As I think you see, or more than half see, μὴ μετὰ κακίας, δόξης δὲ μᾶλλον ἁμαρτίᾳ (to be taken together, “not with ill intent but rather by error of judgment”) does not really apply to their now venturing on a course the opposite of their earlier policy of disengagement (τῇ πρότερον ἀπραγμοσύνῃ ἐναντία τολμῶμεν), as the grammar itself would suggest it does, but is instead to be understood as applying to that απραγμοσυνη, proffering a de facto excuse and apology for their prior isolationism.
This syntactical compactness and ellipticality (the adverbial phrases applying to the following abstract noun) is a relatively mild example of Thucydides stretching the resources of the Greek language beyond its normal bounds.
Smaller points:
ξυγγνώμη without an accompanying verb is unusual (appreciably more so than αναγκη heading the preceding main clause, but assisted by that) but intelligible enough in context.
κακία may encompass moral failure and cowardice as well as evil intent—it’s probably not to be pinned down. Similarly with τολμῶμεν. απραγμοσυνη seems to have been something of a political buzzword.
A plainer, more conventional writer would have used αλλα rather than δε, effecting a straightforward opposition between κακια and δοξης αμαρτια, which themselves would not have been given such variation of phrasing. That’s just a stylistic point.
Thank you mwh for so generously explaining. This sentence so baffled me that I’ll study it again with your critique in view.
While I was working on this sentence, I never asked, “What exactly is the ξυγγνώμη (forgiveness) meant to be for: the past isolation, or the present suit for alliance?”
As I think now, with the information I have, the peril to the Corcyraeans is the obvious motive for their suit for an alliance, just as the envoy says. Hence it is their past policy for which they want pardon. By peeking ahead in the text, I note that the Corinthians will have their say before the Athenians. It will be interesting to see how they reply to this present oration.
Ostensibly they seek forgiveness for making so bold (τολμῶμεν) as to propose alliance, in reversal of their non-alignment principles. But they make it clear that they’re apologizing for their past isolationism, which is no longer sustainable. The main thrust of their speech is of course to argue that it’s in the Athenians’ self-interests to agree to alliance with them.
I’m tempted to propose ξυγγνώμης genitive, in tandem with επικουρίας, but I suppose the syntactically more difficult nominative is rhetorically stronger.
And yes, the Corinthians proceed to a point-by-point rebuttal (I’ve just read through it), forcibly inviting direct comparison of the two speeches. Which will the Athenians find more persuasive, we wonder, and on what grounds?