 The criterion of non-circularity seems to follow straightforwardly from the conception of definition on which a definition is supposed to lay down a distinguishing property of a kind K, which in turn can help us distinguish instances of K from all other objects. This seems to entail that the definition of K can’t appeal directly or indirectly back to K itself; for then it would be unhelpful when it comes to distinguishing instances of K from other entities. But if the purpose of a definition is to capture the application-conditions of the definiendum term, then the criterion of non-circularity doesn’t make much sense; for the concept on the basis of which the definiendum term is used might be unanalyzable independently of itself, so no non-circular definition might be available for it.