  In his work, Mayr relates different approaches to the species concept to the philosophical distinction between essentialism and nominalism. He associates essentialism with the view that a species concept refers to a universal or type. This view of the referent of the concept leads to the Typological Species Concept, which he traces from Linnaeus back to Plato and Aristotle, and which he claims ‘is now universally abandoned’ (1976 516). It is worth noting that serious doubt has been cast both on the historical and the philosophical credentials of Mayr’s ‘Typological Species Concept’ (see, e.g. Lennox, 1987; repr. in Lennox 2001b; Winsor 2001, 2006; Walsh 2006; Wilkins 2009). At the opposite extreme is nominalism, which combines the view that only individuals exist in nature and that species are concepts invented for the purpose of grouping these individuals collectively.