So what if we assume the truth of the no-one-world view of things (as described in my earlier posting No Objective View: 5th Installment). What is the guarantor of the rightness of our depictions of the world? Our criteria of rightness. We adopt different criteria, weighted in different ways. I like using reason, consistency, appeal to evidence, always being open to questioning assumptions. Others might appeal more to faith, or experience, or the power of rhetoric, or common sense, or tradition, or they give a different priority to the criteria I use, perhaps non-contradiction is not as important to them as is empirical confirmation. (Graham Priest describes the way different criteria that scientific investigators use are weighted, so that consistency or non-contradictoriness may not be what’s of paramount importance.)
When situations arise where we have to engage others about what is right and what to do, we have to, according to my approach (of course their’s might be different and that would then be part of the topic of conversation), be clear about what is believed, what point is being discussed, why we believe what we believe and what criteria we use to validate our beliefs and what criteria we think should be used to validate beliefs and why. The ideal discussion would press forward into each area as it arose. For example, differences over evidence might have to be pursued. That might mean investigating the validity of sources. That might lead to a discussion of the methods those sources use to collect evidence. That might lead to a discussion of how we rate different methods. And so on.
If the discussion was sustained long enough we’d probably have to see what criteria we share in common and what criteria we don’t and give reasons for our criteria. At some point we both won’t be able to defend our criteria any further, we’ll reach a point where we just made an existential choice to believe or assume things. The discussion could end there or, I propose, if the parties are willing, the nature of our attachment to our belief; the psychological reasons why we are attached to particular criteria and beliefs can be investigated. For example, why is consistency so important to me? It’s only one of a number, and perhaps not the most important, criteria of validity. There’s also corresponding with the evidence, plausibility of explanation, simplicity. Why am I not a Whitmanian embracer of contradictions as Marshall McLuhan appeared to be? This has to do with the nature of my person, it can be investigated after argumentation reached its limits.