"Amid the welter of vague political abstractions ... where meanings shift so quickly and so subtly, not only following changes of thought, but often manipulated artificially by political practitioners so as to obscure, expand, or distort ... a certain broad consistency in its relations to other kindred terms is the nearest approach to definition which such a term as Imperialism admits. Nationalism, internationalism, colonialism, its three closest congeners, are equally elusive, equally shifty, and the changeful overlapping of all four demands the closest vigilance."