Rethinking emotion as a natural kind: Correctives from Spinoza and hierarchical homology

It is commonly claimed that the folk category of emotion does not constitute a natural kind, due to the significant compositional differences between its members, especially basic and complex emotions. Arguably, however, this conclusion stems from the dualistic philosophical anthropology underlying the discussion, which presupposes a metaphysical "split" between mind and body. This is the case irrespective of whether a traditional or biological (homology-based) approach to natural kinds is adopted. Since the origins of this increasingly disputed anthropology can ultimately be traced to Descartes' substance dualism, its adverse effects can likewise be addressed using a contemporary theory of emotion developed from Spinoza, one of Descartes' earliest critics on this issue. Furthermore, a Spinozistic view of emotion accords with the recent shift to a hierarchical approach to homology, which recognises that the evolutionary lineage of complex biological units should be traced via relational qualities rather than physical characteristics. Both the Spinozistic approach to emotion and the hierarchical approach to homology show that the compositional variation in the folk category of emotion does not necessarily preclude it from constituting a natural kind.