Your opponent has answered “Yes” to the question “Can I change your mind?” (and means it). Most of us can’t. Many more of us say we can if only so-and-so could prove XYZ. Once we’re shown XYZ is proven we immediately bring up esoteric notions about what actually constitutes evidence and proof, want to know who funded the study that proved XYZ, and generally do anything we can to not actually change our mind.
You’re willing to accept the same evidence from your opponent that you require. Number 1 above is more or less fine if we also let our opponent get away with the same sloppiness. The left admonishes the right for not believing in climate change, but continues to be suspicious of GMOs despite similar universal evidence (all the same national and international organizations with white papers on the negative consequences of climate change have position papers that are pro-GMO). My position is that we are human and thus all inconsistent and so we should not be so hard on others for being so. Admitting our inconsistency and emotional nature can let us have a more honest conversation about our beliefs that are not masked in “facts” and “evidence.”
You can answer a series of the next obvious questions about your position. For example, if you believe the rich should pay more in taxes you should know how much they currently pay in taxes. If you believe we should have fewer refugees you should know how many we currently have. Many people think they know the answers to these questions and actually don’t. If “Warren Buffet’s secretary pays more in taxes than he does” is the mental model you have for high earners under the U.S. tax system please humbly have a seat.
You can pass an Ideological Turing Test. Meaning that if we put you behind a curtain you could fairly and accurately represent the views of your opponent. You should not, for example, say, “The rich believe they shouldn’t be taxed much because everything trickles down to the rest of us and there’s nothing wrong with the masses fighting ever harder for the few remaining scraps” or “Liberals believe most immigrants should be let into the country with very little screening, live off of welfare until they get a job, all so they can have more fake pseudo-intellectual conversations with foreigners at their bohemian dinner parties.” Or anything approaching those two positions. Almost every position has a very reasonable line of argumentation based on experiences and ethics of those that believe it.
You know what it would mean if you were wrong. What if the minimum wage was genuinely bad for poor people? What would that mean for your identity and life experience and the friends you have and the things you do? What if gay people really were born that way? Or what if sexuality was actually all a choice? What if climate change was real and a serious threat to future human survival? What if taking steroids didn’t really help Barry Bonds that much? If you can’t honestly imagine all the ways your life and identity are tied up in believing what you believe you’ll never be able to have an honest conversation.
You know why you need other people to believe the same thing you believe. You want to say that it’s because people’s lives are at stake. And sometimes that’s true. I’m not arguing there is never a time to fight. But many people’s beliefs seem devoted to signaling as much as to helping people. Not everyone has to agree with you. You might be wrong, remember. Often, time spent convincing people to believe what you believe is not only fruitless, but takes away time you could be spending addressing the problem. Let people disagree with you and love them anyway, admit you might be wrong, and push ahead humbly.
If you failed any one of these tests, and especially if you passed all of them, perhaps you should listen to, and empathize with, your opponent; not actually call them your “opponent” to begin with; and spend as much time questioning your own views as those you disagree with. This not simply so you can feel warm and fuzzy, although you will, but because it’s probably a much better approach for being persuasive out in the wild.