International Relations are the billiard table, and the states are the balls, which keep on banging one against the other: states internal properties do not influence the effect of the clash. This is the most effective metaphor that neo-realism provides to explain its own essence: states are like billiard balls, not only because they constantly clash, but more because - assumed to be solid - the domestic configuration gives no information about their behaviour in the inter-state system (J. M. Hobson, 2001: 401).
In other words, "the fundamental unit in the system is the sovereign state. States are entities with a delimited territory, a stable population and a government. Sovereignty means constitutional independence, that is, independent, centralised authority over a specific territory and population. [ ] the sovereign state border is a legal, juridical construct. It has never prevented a wide range of substantial connections between different societies, in the political, economic, social, cultural, technological, and other areas. The consequence of that is clear: what we at a given time consider domestic is the result of a previous interplay between domestic and international- (James A.1986, cited in Søresen 2001: 12).
This is exactly the view of the state that Waltz wants to give: states are to be considered as undifferentiated units, because they are functionally alike. In fact, they are all sovereign entities which hold both means of violence and of rule-making, means that serve for the promotion of their own survival in a world of competing states. It is clear that this view is a reproduction of the Hobbes' state of nature' in which the only daily certainty is the war of all against all'. Men are considered evil and selfish creatures who fight for their own survival and dominance on the others in a condition of total anarchy: self-help is the only rule (Viotti and Kauppi, 1993: 40-41).
