People will tell you that online discussion rarely amounts to anything more than futile debate. Some even believe it enough to avoid getting into one. Those aren't my people.
I'd even go so far as to say that online discussion can be worthwhile, but you have to know where to draw the line. The more quickly you can identify an unproductive discussion, the sooner you can extricate yourself from it and devote your time to some more constructive pursuit.
What we'll want, then, is some heuristic for distinguishing a discussion conducted in bad faith from those with real potential. One way to do so is by looking for brown M&Ms.
Does that read like nonsense? Maybe a little context is in order.
The Van Halen Rider
When entertainers sign contracts to perform, they sometimes include "riders" with a list of items to be provided backstage. The bigger the entertainer, the more outlandish the rider can become. Van Halen's rider used to include a clause that required the promoter to provide a bowl of M&Ms with all of the brown pieces removed. If the band showed up and that bowl wasn't there, or if it contained the verboten color, the band would walk, leaving the promoter in the lurch.
Van Halen's rider was the stuff of rock legend for a long time, because it seemed to illustrate what prima donas famous musicians could be. The brown M&M clause really was on the band's backstage rider, though, and as it turns out, they had a pretty compelling explanation for it.
The short version is that, like a lot of arena rock concerts from the 80s and 90s, Van Halen shows could be wildly dangerous if not assembled correctly. The brown M&M clause was a test of the promoter's attention to detail. If they couldn't get a relatively simply clause like "no brown M&Ms" right, there was a good chance that they had skimped on details of much greater consequence. Including that item on the rider gave the band an easy litmus for testing that their business had been conducted in good faith.
A Rider for Online Discussion
There may not be quite as much at stake in an online conversation as in a pyrotechnic display, but it's still an investment of time and effort. The more you're asked to invest, the more reasonable it is to want some assurance that it will be conducted in good faith.
One way to test for bad faith is by asking a question that serves as the conversational equivalent of Van Halen's brown M&M rider. Not just any question will do, though. To serve its intended purpose, it must be:
Challenging: The best questions will tend to be those that point to a dilemma in the other party's position.
Simple: Questions with binary answers (e.g. "yes" or "no") are best; avoid open-ended "how" and "why" questions. The more complicated your question, the harder it will be to distinguish genuine answers from clever evasions.
Pertinent: The test only works if you don't give the other party just grounds for evading your question. Even an innocuous question can seem like sophistry if its relevance to the topic at hand is unclear.
Fair: Your goal here is to get a good faith response, so don't preclude it by giving the other party reason for wariness.
In other words, you want a straightforward and defensible question that could be taken to compromise the other person's position. It doesn't need to be a coup de grace — in fact, the best dilemmas are those that a reasonable person could potentially address — but the test doesn't work unless the other party is at least a little reluctant to answer.
If you're sure that you've met all of those requirements, then what you need to know is: How does the other party deal with that reluctance?
A person arguing in good faith may want to avoid the question, but if it's genuinely fair, pertinent and straightforward, they'll be honor-bound to address it sooner or later. A person arguing in bad faith, on the other hand, will attempt to turn the question around on you, call it illegitimate, impugn your motives, or otherwise try to steer the focus away from it. If they repeatedly refuse to answer, then you can excuse yourself without worrying that you could have done something to salvage the discussion. Chances are, there was never a real discussion there to salvage.
Why does this work?
Because real dialogue (as opposed to pro forma debate) involves give and take. What you're checking for here is the other person's willingness to give as well as take. If the other party is trolling you, or cares only about the appearance of having won the argument, then they'll work to dictate the terms of discussion. The proverbial brown M&M, so to speak, is a refusal to accept a reasonable term that doesn't tilt the balance entirely in their favor.
The mechanism that makes the test work, though, is your insistence. After the first deflection, turn the other party back to the question you asked. If deflected again, be explicit about it: you don't intend to address other points or questions until they've addressed yours. Give them several chances to demonstrate their willingness to meet you half way, but the more they resist addressing the question, the less obligated you should feel to stay involved. A person arguing in bad faith will say or do practically anything to avoid answering a question that genuinely challenges their position — anything, that is, except end the dialogue. That part is up to you.
That said, there are a few cautions you should bear in mind:
Not all discussions need testing. In friendly or official situations, it can even be rude to demand a demonstration of good faith. Only look for brown M&Ms when (a) you suspect that the other party intends to dictate terms in their favor, and (b) you're sure they don't have a right to do so.
It's possible to get this wrong. If the other party objects to your question, give that objection serious thought before you declare it a brown M&M. It's always possible that the objection is justified, and not just an attempt to deflect. If you'll seize on any opportunity to dismiss the other person, then…
You might be the one arguing in bad faith. Dialogue requires good faith on both sides. Testing the other person doesn't help if you're the problem. In the wrong hands, the principle of the brown M&M can be used to short circuit an otherwise constructive discussion. To that end, be sure to…
Issue a challenge, not a trap. Your hope should be to get a good faith response, not a bad one. Don't preclude that by giving the other party reason to suspect your motives. That shouldn't mean that there are no logical consequences for answering one way rather than another, but those consequences should be obvious enough that the other person can take them into consideration before answering.
The test ends when either side moves. By giving you an honest answer (even if it's not the honest answer you wanted), the other party signals their willingness to keep the discussion moving on equal terms. Be willing to move on with them. On the other hand, if you let them steer you to another question or topic without holding them to the task of answering your own, you'll have to bide your time for another chance to test their good faith.
One final (but important) caution remains to be made: The brown M&M has no logical force. You can't disprove another person's position by asking a question they refuse to answer. Nor does your position "win" the argument when you decide that the other has been argued in bad faith. The only thing you can hope to gain by this test is the time and happiness you would have lost by committing to a discussion with little or no possibility of a constructive end. Sometimes, though, the rest of your day is the most valuable prize you could reasonably expect.