  That type of challenge can in turn take different forms. A straightforward way to argue that an argument is self-defeating is to show that its advocates are committed to claims that are outright inconsistent with it (i.e., either with its conclusion or with its premises). Consider for example an argument which is aimed at establishing the error-theoretical thesis that all moral claims are false. If that argument can be extended to metaethics, so that it commits its advocates to thinking that all metaethical claims are false as well (including the error theory), then they have obviously ended up in an awkward place.