On Common Sense, Estimation, and the Soul’s Unity in Avicenna

This paper addresses two questions related to Themistius’ alleged influence on Avicenna’s theory of the common sense. The first question concerns the phenomenon of incidental perception, which Themistius explained by means of the common sense. For Avicenna, on the contrary, the explanation of cases like our perceiving something yellow as honey involves the faculty of estimation and the entire system of the internal senses that he coined, and this results in an analysis that is considerably more complex than Themistius’. The second question concerns Themistius’ claim according to which an incorporeal spirit is the primary subject of perception. I argue that Avicenna departs from such a view both because for him spirit is a corporeal substance and because he insists that the subject of all cognition is the soul, not any of its faculties. Finally, I conclude by briefly considering other, more general ways in which Themistius could have influenced Avicenna’s psychology.