And yet we aren't even united on a common definition of what constitutes ecumenism. "Ecumenism" is a term that gets tossed around a lot in online debates, particularly as a pejorative for things we don't like, but I'm not sure anyone even knows what ecumenism is.
I've given it a rough-draft-shot before (such as here
), but I'd probably have to go back and reread a good amount of the literature to get something more specific. I think it's certainly possible to come up with something that I'd find satisfactory. Coming up with something almost everyone would find satisfactory, though? Doubtful. Then again, almost no one has actually taken the time to read the literature we're talking about, so we'd be approaching the validity of the definition/description from two very different places.
Not going to happen. Some EOs think that outreach toward anyone, even OOs, is heretical. Others think it's fine if it's outreach to OOs but heretical if it's to Catholics. Still others are fine with outreach to Catholics, just not to Anglicans, Lutherans, Methodists, etc.
I've read probably a couple hundred EO traditionalist articles and books, and I've rarely, if ever, come across this. They may disagree as to what proper outreach consists of, but I've not generally heard anyone say that you simply can't talk to group X or Y because it'd be heretical to do so. At most they'll say "You can tell X they're heretical and give the reasons why, then you stop talking".
I can't see how you'd come to one precise definition of "ecumenism".
EDIT--After thinking about it, I suppose it'd naive of me to think anyone would agree to, well, anything
We can't agree on definitions for words like truth, religion, etc., so why would I think anyone would agree about ecumenism, or "outreach" for that matter. Meh...