John Buridan on the Question of the Unity of the Human Being

Is a human being something that is one per se, or are humans composed of two independent substances? Treating the soul as the form of an organic body seems to offer one way of addressing the difficulty. But the debates about the nature of the soul which began to emerge in the 1270s made this question problematic. This article considers Buridan's solution to the problem of how to unify what is corporeal and divisible on the one hand with what is incorporeal and indivisible on the other. Beginning with sensation, which concerns the unity of the sensitive soul and sense data, we turn to the act of thinking, where the intellective soul is united with the image or phantasm qua mover, leading to the realization that the unity of a human being is no longer self-evident. To solve the problem, Buridan takes up and transforms ways of thinking about the human soul inherited from older debates around Averroist psychology, such as the theory of two subjects and the conjunction of the sensible with the intelligible during cognitive activity.