This paper articulates and defends a novel view of the strict distinction that Aristotle makes between human and non-human mental life. We examine two crucially relevant but overlooked arguments that turn on the human capacity for reasoning and inference (syl/logismos) to reconstruct his view of what makes some cognitive processes rational and how they differ from non-rational counterparts. A creature is rational just in case its occurrent cognitive states exhibit a sequential coherence wherein prior cognitive activity constrains subsequent activity for (...) the sake of attaining truth. Processes are rational, then, in virtue of how constituent states relate to each other, not whether any given state involves some peculiar content or grasps some distinct object. This study aids, but does not exhaust, a systematic examination of the rational soul in Aristotle’s writing, based on (a) the human/animal comparisons through which he often elucidates rational cognitive capacities and (b) the distinctions that he draws between elements of rational cognition and non-rational counterparts in terms of what minimally suffices to distinguish between them. (shrink)