Another aspect to questions of 'orthodoxy' concerns the tightness of any definition, not just with respect to writing a dictionary but importantly in respect of fellowship: with whom will I fellowship on the basis of shared commitment to common truth?
The other day these two analogies came to my mind, relating to the search for a spouse.
Some people looking for a spouse (analogy to 'other Christians with whom I will fellowship') have a set of criteria in their mind, perhaps even buried in the subconscious. Must be beautiful/handsome, brainy (but less so than me), established career, same life goals, values and beliefs, and ... ideally someone who so shares my mind that we never argue, and must be pure and unspotted with respect to the past.
Others looking for a spouse are less fussy. Must be a reasonable looker, not dumb (certainly not as dumb as me), think they know where their life is going, similar life goals, values, and believes, ... ideally not too argumentative, but I guess we will have some difference, and, let's be realistic these days, at least 'over' whatever has happened in the past.
One of the difficulties in the world of conservative Anglicanism these days is we have quite a few people acting out the former scenario. At the moment that's taking them away from the Anglican Communion (too messy, not very pure, lack of common mind, too many arguments). But if there is a new 'marriage' will it last? That search for a completely common mind is well, as one of our beer ads used to say, 'It's a hard road finding the perfect woman, son!'
Personally I accept that orthodoxy needs a certain breadth rather than tightness in its definition if I am to fellowship with more people than can fit in a telephone box. Brian McLaren coined the term 'generous orthodoxy'. Perhaps an associated phrase could be 'messy orthodoxy'! Some of us conservatives need to think carefully about our criteria for fellowship. The first scenario above is attractive: it fits with Scripture's teaching on contending for the truth, and with current mantras about truth being more important than unity. But the second is more workable. Yes, it leaves open questions of bounds to 'messy orthodoxy', but it brings to the table a greater willingness to really truly and deeply engage in dialogue. To say nothing of the possibility of a longer lasting marriage!