Abstract
This article considers Avicenna’s insistence on the disunity between the souls of humans, animals, and plants and the mixed elemental bodies in which they inhere. In particular, it looks at (1) why Avicenna rejects their unity and (2) why this rejection, pace some contemporary scholars, is compatible with the status of these souls as substances. I show that both points derive from the causal role that these souls and the elements play in the coming to be and passing away of mixed elemental bodies.