Neorealism shuns classical realism's use of often essentialist concepts such as "human nature" to explain international politics. Instead, neorealist thinkers developed a theory that privileges structural constraints over agents' strategies and motivations.
The international structure is decentralized, having no central authority and is anarchic, with states acting as independent sovereign political units. States are assumed at a minimum to want to ensure their own survival as this is a prerequisite to pursue other goals. This driving force of survival is the primary factor influencing their behaviour and in turn ensures states develop offensive military capabilities, as a mean to increase their relative power. Neorealists bring attention to a persistent lack of trust between states which requires states to be on guard and act in an overtly aggressive manner.
States are deemed similar in terms of needs but not in capabilities for achieving them. The positional placement of states in terms of abilities primarily defines the structure. The structure then limits cooperation among states through fears of relative gains made by other states, and the possibility of dependence on other states. The desire and relative abilities of each state to maximize power results in a 'balance of power', which shapes international relations. It also gives rise to the 'security dilemma' that all nations face.
Neorealists conclude that because violence is part of the structure of the international system it is likely to continue in the future. Indeed, neorealists often argue that the international system has not fundamentally changed from the time of Thucydides to the advent of nuclear warfare. The view that long-lasting peace is not likely to be achieved is described by other theorists as a largely pessimistic view of international relations. One of the main challenges is the democratic peace theory and supporting research such as the book Never at War. Nevertheless such theories have been disregarded by neorealists because they state these theories tend to pick and choose the definition of democracy to get the wanted result. For example Germany of Kaiser Wilhem II, the Dominican Republic of Juan Bosch, or Chile of Salvador Allende are not considered to be democratic or the conflicts do not qualify as wars according to these theorists. Furthermore they claim several wars between democratic states have been averted only by causes other than democratic ones. (see K. WALTZ, "Structural Realism after the Cold War" in International Security, Vol. 25, (2000), 1.)

Criticism

Neorealism has been criticized from the point of view of the philosophy of science. John Vasquez uses the Lakatosian criteria of the Methodology of Scientific Research Programs in an attempt to prove the degenrative nature of the neorealist research program. Thus, Waltz's theory of neorealism explains international behaviour through the balance-of-power concept, according to which states in alsmot all cases balance each other in order to survive. Stephen Walt, on the other hand, argues that states do not balance power, but there is a so-called balance-of-threat, thus always balancing states which seem to be the most threatening, no t necessarily the most powerful. Randall Schweller introduces the concept of balance-of-interests, better known as bandwagoning. Thomas J. Christensen and Jack Snyder try to correct gaps in Waltz's original theory by using the concepts of buck-passing and chain-ganging. However these similar tehories contradict each other, at least partially: for example balancing versus bandwagoning. Vasquez considers them as theoryshifts which explain away discrepant evidence. These contradictory hypotheses increase the probability that at least one passes an empirical test, thus the whole neorealist research program showing signs of degeneration. (Vasquez, John 1997:"The Realist Paradigm and Degenerative versus Progressive Research Programs". In: American Political Science Review, 39(December):899-912)

Notable neorealists

• Barry Buzan
• Robert Gilpin
• Joseph Grieco
• Robert Jervis
• John Mearsheimer
• Jack Snyder
• Stephen Walt
• Kenneth Waltz

Courtesy: Wikipedia