Term due to the 20th-century philosopher J. L. Mackie, describing a theory according to which everyday thought in some area is sufficiently infected by mistaken philosophical views to be widely in error. Mackie believed that ordinary moral thinking involved belief in an objective, rationally compelling property of ‘to-be-doneness’ in things, but that this belief cannot be defended. An error theory stands directly opposed to the Wittgensteinian view that ordinary language is perfectly in order as it is, and that only philosophical thought about it gives rise to confusion. The principal problem confronting an error theory is to say how our thinking ought to be remedied to free us of the error. One suggestion is wholesale eliminativism, counselling us to abandon the area entirely; other less radical moves would counsel various cleaning-up operations. See also quasi-realism.