This article addresses the relationship between understanding and believing from the cognitive perspective of information-processing. I promote, within the scope of the Critical Discourse Analysis agenda, the relevance of an account of belief-fixation sustained by a combination of argumentative and cognitive insights. To this end, I first argue that discursive strategies fulfilling legitimization purposes, such as evidentials (see Hart, this issue), tap into the same cognitive mechanisms as (both sound and fallacious) arguments. I then proceed to examine the idea that the most effective arguments are the ones that manage to obscure or make irrelevant counter-evidence and propose, from a cognitive pragmatic perspective, a formulation of rhetorical effectiveness as a constraint on information-selection taking place at the interpretation stage and decisively influencing the evaluation stage responsible for belief-fixation. © The Author(s) 2011.