In PA IV.10 Aristotle explains the upright posture of human beings with reference to physiological factors that determine the abilities to think and behave intelligently. A detailed interpretation of Aristotle's explanation is supplied by drawing on his physiological theory and contrasting it with Plato‗s explanation of human posture in the Timaeus. In the crucial passage Aristotle seems to couple ‘thinking’ with the rational capacity of the soul and ‘intelligence’ with the common sense. It is argued that the phrase ‘common sense’ is best taken with reference to the sensory capacity of the soul, that is the capacity of the soul which comprises perception and imagination. This capacity exhausts the cognitive repertoire of non-rational animals, and it accounts for their intelligent behaviour. In the next two chapters it will be argued that Aristotle uses the phrase koine aisthesis two more times in the same way, as a proper name for the sensory capacity of the soul, both times in the context of complex non-rational cognitive activities.
Keywords: De Partibus Animalium, Plato, Timaeus, common sense, animals, human beings, posture, cognitive capacities, non-rational, koine aisthesis