My position as a materialist (and a practicing scientist) is that propositions are not magical transcendental objects. The idea of "refutation" rests on the presupposition of a given linguistic exchange being inside a self-consistent system of argument. In reality, language behaviors, including writing and argument, are always material, contingent and underspecified. Language is a "reef of dead metaphors". Utterances take place in a cultural and historical context, and their meaning, both at the level of reference and argument structure, is always dependent on that context, <i>including what I am writing right now</i>. You run into this kind of boring infinite recursion refrain when you remain attached to the idea that "proof" and "truth" operate at a metaphysical level above material. It's unfortunate that this is so widespread.