 We saw above that for the subject-matter in question the error-theorist agrees with the realist that the truth of the atomic, declarative sentences of that area requires the existence of the relevant type of objects, or the instantiation of the relevant sorts of properties. Although the realist and the error-theorist agree on this much, they of course disagree on the question of whether the relevant type of objects exist, or on whether the relevant sorts of properties are instantiated: the error-theorist claims that they don’t, so that the atomic, declarative sentences of the area are systematically and uniformly false, the realist claims that at least in some instances the relevant objects exist or the relevant properties are instantiated, so that the atomic, declarative sentences of the area are at least in some instances true. We also saw that an error-theory about a particular area could be motivated by epistemological worries (Field) or by a combination of epistemological and metaphysical worries (Mackie).