 Yet another problem for species as the model of sortals is that most philosophers of biology now agree that species don’t have essences, though there is disagreement among them about the best way to characterize species (for details, see the entry on species). A rejection of species essentialism doesn’t necessarily carry a rejection of the essentialism Wiggins has advocated. His is individual essentialism, i.e., the view that an individual is essentially a member of the species it belongs to (Wiggins 2001, chap. 4). Thus, a given whale, for example, is essentially a member of the species whales; this even in the case where there is no essential property such a species possesses. Moreover, there are attempts by Wiggins to argue that species don’t have essences. He states, for example, that species is an: