While realism as a formal discipline in international relations did not arrive until
World War II, its primary assumptions have been expressed in earlier writings. Realists trace the history of their ideas back to
classical antiquity, beginning with
Thucydides ( 5th century BCE). Historian
Jean Bethke Elshtain traces the historiography of realism: :The genealogy of realism as international relations, although acknowledging antecedents, gets down to serious business with Machiavelli, moving on to theorists of sovereignty and apologists for the national interest. It is present in its early modern forms with Hobbes's
Leviathan (1651). Modern realism began as a serious field of research in the United States during and after World War II. This evolution was partly fueled by European war migrants like
Hans Morgenthau, whose work
Politics Among Nations is considered a seminal development in the rise of modern realism. Other influential figures were
George F. Kennan (known for his work on
containment),
Nicholas Spykman (known for his work on
geostrategy and
containment),
Herman Kahn (known for his work on
nuclear strategy) and
E. H. Carr.
Classical realism Classical realism states that it is fundamentally the nature of humans that pushes states and individuals to act in a way that places interests over ideologies. Classical realism is an ideology defined as the view that the "drive for power and the will to dominate [that are] held to be fundamental aspects of human nature". Prominent classical realists: •
E. H. Carr •
Hans Morgenthau •
Reinhold Niebuhr – Christian realism •
Raymond Aron •
George Kennan Liberal realism or the English school of rationalism The English school holds that the international system, while anarchical in structure, forms a "society of states" where common norms and interests allow for more order and stability than that which may be expected in a strict realist view. Prominent English School writer
Hedley Bull's 1977 classic,
The Anarchical Society, is a key statement of this position. Prominent liberal realists: •
Hedley Bull – argued for both the existence of an international society of states and its perseverance even in times of great systemic upheaval, meaning regional or so-called "world wars" •
Martin Wight •
Barry Buzan Neorealism or structural realism Neorealism derives from classical realism except that instead of human nature, its focus is predominantly on the anarchic structure of the international system. States are primary actors because there is no political monopoly on force existing above any sovereign. While states remain the principal actors, greater attention is given to the forces above and below the states through
levels of analysis or
structure and agency debate. The international system is seen as a structure acting on the state with individuals below the level of the state acting as agency on the state as a whole. While neorealism shares a focus on the international system with the English school, neorealism differs in the emphasis it places on the permanence of conflict. To ensure state security, states must be on constant preparation for conflict through economic and military build-up. Prominent neorealists: •
Robert J. Art –
neorealism •
Robert Gilpin –
hegemonic theory •
Robert Jervis –
defensive realism •
John Mearsheimer –
offensive realism •
Barry Posen –
neorealism •
Kenneth Waltz –
defensive realism •
Stephen Walt –
defensive realism Neoclassical realism Neoclassical realism can be seen as the third generation of realism, coming after the classical authors of the first wave (
Thucydides,
Niccolò Machiavelli,
Thomas Hobbes) and the neorealists (especially
Kenneth Waltz). Its designation of "neoclassical", then, has a double meaning: • It offers the classics a renaissance; • It is a synthesis of the neorealist and the classical realist approaches.
Gideon Rose is responsible for coining the term in a book review he wrote in 1998. The primary motivation underlying the development of neoclassical realism was that neorealism was only useful to explain political outcomes (classified as being theories of international politics), but had nothing to offer about particular states' behavior (or theories of
foreign policy). The basic approach, then, was for these authors to "refine, not refute, Kenneth Waltz", by adding domestic intervening variables between systemic incentives and a state's foreign policy decision. Thus, the basic theoretical architecture of neoclassical realism is: : Distribution of power in the international system (
independent variable) : Domestic perception of the system and domestic incentives (
intervening variable) : Foreign policy decision (
dependent variable) While neoclassical realism has only been used for theories of foreign policy so far,
Randall Schweller notes that it could be useful to explain certain types of political outcomes as well. Neoclassical realism is particularly appealing from a research standpoint because it still retains a lot of the theoretical rigor that Waltz has brought to realism, but at the same time can easily incorporate a content-rich analysis, since its main method for testing theories is the process-tracing of case studies. Prominent neoclassical realists: Similarly,
Jennifer Sterling-Folker has argued that theoretical synthesis helps explanations of international monetary policy by combining realism's emphasis of an anarchic system with constructivism's insights regarding important factors from the domestic level. Scholars such as Oded Löwenheim and
Ned Lebow have also been associated with realist constructivism.
Regional neorealism An international relations theory proposed by
Anthony Heron.. It builds on classical and structural realist traditions by arguing that states respond primarily to security pressures within their regional environment rather than to the global system as a whole. The framework suggests that regional security structures possess their own polarity, threat hierarchies, and power distributions that can diverge from global-level dynamics. Heron's approach departs from traditional
neorealism, which treats the international system as a single, uniform structure defined by global anarchy. Regional neorealism instead conceptualises the system as a set of overlapping regional security architectures that exert distinct constraints on state behaviour. According to the theory, geography, resource distribution, and the density of local institutions create region-specific structural logics. States experience incentives produced by both global and regional structures, but regional pressures are considered more immediate and behaviour-shaping. The theory conforms with both concepts of
defensive and
offensive realism, suggesting that regional factors alone determine whether conflict between states exhibits traits of each school. Heron developed the framework in response to empirical cases during his scholarly work on the Arctic, where states acted contrary to predictions derived from global-level structural incentives, particularly in medium-power regions. ==Criticisms==