Kenneth Neal Waltz (1924-2013) revolutionized the study of international relations with a simple but powerful insight: the behavior of states is determined not primarily by human nature or the characteristics of individual states, but by the structure of the international system itself. His “structural realism” or “neorealism,” developed most fully in “Theory of International Politics” (1979), became the dominant theoretical framework in the field and remains essential for understanding how scholars think about international relations.
Waltz combined scientific rigor with theoretical ambition. He sought to create a genuine theory of international politics—not just description or historical analysis, but a logically coherent framework that could explain and predict state behavior. Whether one accepts his theory or not, engagement with Waltz is unavoidable. He set the terms of debate for a generation.
The Person¶
Academic Formation¶
Waltz’s intellectual path was unconventional:
- World War II service in the Army interrupted his education
- Completed undergraduate work at Oberlin College
- PhD from Columbia University (1954) under William T.R. Fox
- Taught at Columbia, Swarthmore, Brandeis, and Berkeley
- Spent his career building theory rather than accumulating case studies
He was a theorist by temperament, more interested in logical structures than in empirical details.
Intellectual Temperament¶
Colleagues described Waltz as:
- Rigorous and demanding in argument
- Spare and economical in prose
- Skeptical of intellectual fashion
- Willing to defend unpopular positions
- Focused on getting the logic right
His writing style reflected his thinking: stripped of ornament, each sentence doing analytical work.
Personal History¶
Waltz maintained that personal experience should not drive theory, but his biography shaped his questions:
- World War II service gave him direct experience of international conflict
- The Cold War provided the context for his theoretical work
- The nuclear revolution raised stakes that demanded rigorous thinking
- Experience with policy debates showed him the limits of ad hoc analysis
Key Ideas¶
The Three Images¶
Waltz’s first book, “Man, the State, and War” (1959), organized thinking about war’s causes into three “images” or levels of analysis:
First Image (Human Nature): War results from human nature—selfishness, stupidity, or aggression. Thinkers like Morgenthau locate the cause of conflict in human psychology.
Second Image (State Structure): War results from the internal organization of states. Some argue democracies are peaceful; others blame capitalist or authoritarian systems.
Third Image (International System): War results from the anarchic structure of international politics. Without world government, states must rely on self-help, generating insecurity and conflict.
Waltz argued the third image is decisive. Human nature and state structure may influence how states behave, but the structure of the international system explains why conflict recurs across different eras, cultures, and regime types.
The Structure of International Politics¶
In “Theory of International Politics,” Waltz developed his structural approach:
Anarchy: The international system lacks a central authority. There is no world government to enforce agreements, punish aggressors, or protect the weak. States exist in a “self-help” system.
Like Units: States are functionally similar—they all must provide for their own security. Despite differences in size, culture, and regime type, states face the same fundamental problem.
Distribution of Capabilities: What varies is the distribution of power among states. Whether the system is unipolar, bipolar, or multipolar shapes state behavior and the likelihood of war.
Why States Seek Power¶
For Waltz, states seek power not because of aggressive human nature but because the system compels them to:
“In anarchy, security is the highest end. Only if survival is assured can states safely seek such other goals as tranquility, profit, and power.”
States that fail to attend to their security will be eliminated or dominated. The system “selects” for states that compete effectively. Even peaceful states must arm and balance against potential threats.
Balancing Behavior¶
A central prediction of structural realism is that states balance against power:
- When one state becomes too powerful, others form alliances to counter it
- This balancing behavior recurs across history
- It operates regardless of ideology, regime type, or individual leaders
- The balance-of-power is the natural condition of international politics
Bipolarity vs. Multipolarity¶
Waltz argued that bipolar systems are more stable than multipolar ones:
Multipolar systems (like pre-WWI Europe) are prone to miscalculation, shifting alliances, and uncertainty about who will fight whom.
Bipolar systems (like the Cold War) are more stable because: - Each superpower focuses on the other - Peripheral conflicts do not threaten the central balance - Capabilities are easier to estimate - Deterrence is simpler
This argument was controversial but influential in Cold War thinking.
Nuclear Weapons and Stability¶
Waltz extended his logic to nuclear weapons:
- Nuclear weapons make the costs of war catastrophic
- Rational states will not fight nuclear wars
- Nuclear deterrence produces stability
- More nuclear weapons (in some cases) might mean less war
In “The Spread of Nuclear Weapons” (with Scott Sagan), Waltz argued nuclear proliferation could be stabilizing—a position that remains deeply controversial.
Major Works¶
“Man, the State, and War” (1959)¶
This theoretical classic organized the field:
- Introduced the “three images” framework
- Surveyed philosophical approaches to war’s causes
- Argued for the primacy of systemic explanation
- Became required reading for generations of students
The book established Waltz as a major theorist.
“Theory of International Politics” (1979)¶
Waltz’s masterwork developed structural realism:
- Articulated the distinction between reductionist and systemic theories
- Specified the structure of international politics (anarchy, like units, distribution of capabilities)
- Derived predictions about balancing, stability, and change
- Set standards for theoretical rigor in the field
The book transformed IR theory and sparked decades of debate.
“The Spread of Nuclear Weapons” (with Scott Sagan, 1981/2003)¶
A debate format book where Waltz argued nuclear proliferation could be stabilizing, while Sagan argued against:
- Waltz: Nuclear weapons produce caution; more may be better
- Sagan: Organizational factors make nuclear accidents likely
- The debate illuminates fundamental questions about deterrence
- Neither position has been definitively refuted
Influence¶
Paradigm Definition¶
Waltz defined what counted as theory in international relations:
- Structural, systemic explanation became the standard
- Other approaches had to justify themselves against neorealism
- The “neo-neo debate” (neorealism vs. neoliberalism) structured the field
- Even critics adopted Waltz’s vocabulary and standards
Policy Relevance¶
Waltz’s ideas shaped policy thinking:
- Balance of power analysis informed Cold War strategy
- Bipolarity arguments influenced assessments of stability
- His nuclear deterrence logic shaped debates about proliferation
- Structural thinking became common in strategic analysis
Generational Impact¶
Waltz trained and influenced numerous scholars:
- Stephen Walt (offensive/defensive realism, balance of threat)
- Barry Posen (sources of military doctrine)
- John Mearsheimer (offensive realism)
- Robert Jervis (psychology and deterrence)
His students became leading figures who extended and modified his framework.
Setting the Agenda¶
Even critics engage on Waltz’s terms:
- Constructivists respond to his materialism
- Liberals challenge his assumptions about cooperation
- Critical theorists attack his positivism
- Democratic peace theorists contest his unit-similarity assumption
The field has moved beyond Waltz, but his questions structure ongoing debate.
Criticisms¶
Offensive vs. Defensive Realism¶
Waltz’s neorealism has been challenged from within realism:
Defensive realists (following Waltz) argue: - States primarily seek security, not power maximization - Balancing behavior restrains expansion - Aggressive states face counterbalancing coalitions
Offensive realists (following Mearsheimer) argue: - States seek to maximize power, not just security - The structure compels aggression, not just defense - Balancing may fail; hegemony is possible
This debate continues within the realist paradigm.
Constructivist Critiques¶
Constructivists argue Waltz:
- Takes state interests as given when they are socially constructed
- Ignores how ideas, norms, and identity shape behavior
- Cannot explain change in international politics
- Treats “anarchy” as having a single logic when its meaning varies
Alexander Wendt’s famous argument that “anarchy is what states make of it” directly challenges Waltz’s structural determinism.
Liberal Institutionalist Critiques¶
Liberals argue Waltz:
- Underestimates the role of international institutions
- Ignores how repeated interaction enables cooperation
- Cannot explain why states cooperate extensively despite anarchy
- Overestimates the constraints of the security dilemma
Robert Keohane’s “After Hegemony” argued institutions can facilitate cooperation even in anarchy.
Empirical Challenges¶
Scholars have challenged Waltz’s predictions:
- Balancing behavior is not as consistent as the theory predicts
- States often “bandwagon” with the strong rather than balance
- Bipolarity did not prevent numerous Cold War crises
- Nuclear proliferation’s effects are contested
Normative Concerns¶
Some argue Waltz’s theory:
- Legitimizes power politics by making it seem natural
- Offers no guidance for improving international relations
- Is deeply conservative, treating change as unlikely
- Abandons the aspiration to transcend conflict
Contemporary Relevance¶
US-China Competition¶
Waltz’s framework applies to contemporary great power competition:
- The distribution of capabilities is shifting toward bipolarity
- Structural pressures generate competition regardless of intentions
- Balancing coalitions (Quad, AUKUS) form against rising power
- Economic interdependence may not prevent security competition
The Ukraine War¶
The war tests neorealist predictions:
- Russia balanced against NATO expansion (as the theory predicts)
- The West provides balancing support to Ukraine
- Nuclear weapons complicate escalation dynamics
- The conflict reflects structural pressures
Nuclear Proliferation¶
Waltz’s controversial nuclear optimism remains relevant:
- North Korea’s nuclear capability affects regional dynamics
- Iran’s potential capability shapes Middle East politics
- The logic of deterrence continues to inform policy
- Whether proliferation stabilizes or destabilizes is debated
The Enduring Security Dilemma¶
Waltz’s concept of the security dilemma remains essential:
- States’ defensive measures threaten others
- Mistrust prevents cooperation even when beneficial
- Arms races result from structure, not malevolence
- This dynamic persists in contemporary relationships
Conclusion¶
Kenneth Waltz gave international relations theory what it had lacked: a parsimonious, logically rigorous framework for understanding why states behave as they do. By locating the cause of conflict in the structure of the international system rather than in human nature or state characteristics, he provided an explanation that applies across historical periods and cultural contexts.
The power of Waltz’s theory lies in its simplicity. A few variables—anarchy, the distribution of capabilities—generate predictions about state behavior that have significant explanatory power. The limitations of his theory—its inability to explain change, its neglect of ideas and identity, its questionable predictions about balancing—have motivated alternative approaches. But these alternatives define themselves in relation to Waltz.
Structural realism will not be the last word in international relations theory. But it represents a standard of theoretical ambition and rigor that subsequent scholars must meet. Waltz asked fundamental questions about why war recurs despite its costs, and he provided answers of enduring significance. The anarchic structure of international politics continues to shape state behavior, and understanding that structure remains essential for anyone who seeks to comprehend—or change—world politics.
Sources & Further Reading¶
Kenneth Waltz, “Theory of International Politics” (1979) - The foundational text of structural realism and one of the most influential works in international relations theory. Dense but essential reading for serious students of the field.
Kenneth Waltz, “Man, the State, and War” (1959) - The accessible introduction to Waltz’s thought, organizing approaches to war’s causes into three “images.” More readable than “Theory of International Politics” and a good starting point.
Robert Keohane, ed., “Neorealism and Its Critics” (1986) - A collection of essays responding to Waltz, including contributions from liberals, constructivists, and defenders. Captures the debate that Waltz’s work generated.
John Mearsheimer, “The Tragedy of Great Power Politics” (2001) - The leading alternative within realism, arguing for “offensive” rather than Waltz’s “defensive” realism. Essential for understanding how realists disagree among themselves.
Alexander Wendt, “Social Theory of International Politics” (1999) - The leading constructivist response to Waltz, arguing that anarchy does not have a single logic and that international politics is shaped by shared ideas, not just material capabilities.