By synthesizing the argumentation theory of new rhetoric with research on heuristics and motivated reasoning, we develop a conceptual view of argumentation based on reasoning motivations that sheds new light on the morality of decision-making. Accordingly, we propose that reasoning in eristic argumentation is motivated by psychological (e.g., anxiety reduction) or material (e.g., vested interests) gains that do not depend on resolving the problem in question truthfully. Contrary to heuristic argumentation, in which disputants genuinely argue to reach a practically rational solution, eristic argumentation aims to defeat the counterparty rather than seeking a reasonable solution. Eristic argumentation is susceptible to arbitrariness and power...