QUOTE : If the process fails at any point, the idea in question lacks cognitive content. When carried through successfully, however, it yields a ‘just definition’ – a precise account of the troublesome idea or term. Hume uses his account of definition in his project’s critical phase to show that the central concepts of traditional metaphysics lack any intelligible content. He also uses it in its constructive phase to determine the precise meaning of our terms and ideas. Our ideas are also regularly connected, and a science of human nature should account for this ‘secret tie or union’ among them. Hume explained this ‘union’ in terms of the mind’s natural ability to associate certain ideas.