Wilson has claimed that he had never meant to imply what "ought" to be, only what "is" the case. However, some critics have argued that the language of sociobiology readily slips from "is" to "ought", an instance of the naturalistic fallacy. Pinker has argued that opposition to stances considered anti-social, such as ethnic nepotism, is based on moral assumptions, meaning that such opposition is not falsifiable by scientific advances. The history of this debate, and others related to it, are covered in detail by , , and .