Significant Realist Thinkers

Kenneth Waltz, Theory of International Politics (1979) Waltz was a defensive realist thinker. Bipolarity, where two major powers are competing for power, is more stable than multipolarity, where many rival powers are competing with each other . Two major powers can negotiate their way to stability more easily than many powers. The international system is in a state of anarchy, with no central authority above nation-state level. Waltz was one of the original founders of neorealism, or structural realism, in international relations theory and later became associated with the school of defensive neorealism. Waltz's theories have been extensively debated within the field of international relations. In Theory of International Politics (1979), Kenneth Waltz modernised IR theory by moving realism away from its unprovable (albeit persuasive) assumptions about human nature. His theoretical contribution was termed ‘neorealism’ or ‘structural realism’ because he emphasised the notion of ‘structure’ in his explanation. Rather than a state’s decisions and actions being based on human nature, they are arrived at via a simple formula. First, all states are constrained by existing in an international anarchic system (this is the structure). Second, any course of action they pursue is based on their relative power when measured against other states. So, Waltz offered a version of realism that recommended that theorists examine the characteristics of the international system for answers rather than delve into flaws in human nature. In doing so, he sparked a new era in IR theory that attempted to use social scientific methods rather than political theory (or philosophical) methods. The difference is that Waltz’s variables (international anarchy, how much power a state has, etc.) can be empirically/physically measured. Ideas like human nature are assumptions based on certain philosophical views that cannot be measured in the same way.


  1. The international system is anarchic: there is no higher central authority that can enforce rules over individual states.

  2. Given this context, states act on the basis of self-help: They operate with the aim of survival and their interactions with other states reflect their desire to survive.

  3. The structure only changes if great powers take actions that will lead to a change. Most states have no power to change the structure. Given this context, states will try to balance against each other because they will try to increase their chance of survival.



Balancing can take two forms: Internal and external. Internal balancing refers to the investment of military power to match up with other states. External balancing refers to the alliance of states to counter a stronger power, or a hegemon. States will choose the weaker of the available coalitions because of the understanding that the stronger side is the one threatening their security.

The structure of the system is mainly based on the distribution of power. In other words, the distribution of power is the main (and sometimes the only) determinant of international outcomes. Since states are concerned with their own security, they try to maximize their relative power with respect to other states.

Waltz’ theory is mainly a critique of “reductionist” theories which look at the behavior of the units in the system (i.e. states) to explain outcomes. Waltz claims that this approach ignores the constraints imposed on state behavior by the international environment. Moreover, there are patterns of international behavior which cannot be explained by differences at the state level. Looking at the structural level variables parsimoniously explain why “dissimilar units behave in similar ways”. The structure socializes individual states to act similarly because it constrains the menu of actions that the states can use to respond to international phenomena.

In his consideration of international institutions, Waltz emphasizes that these are not the main actors in the international system but states are still the principal decision makers. As long as this will be the case, international institutions will not have any significant effect on international outcomes.

Hedley Bull, The Anarchical Society (1977) is a classic work of international relations theory. It is a comprehensive and detailed exploration of the international system and its implications for global politics. Bull argues that the international system is characterized by anarchy, which he defines as the absence of a higher authority to regulate the behavior of states. He then goes on to discuss the implications of this system, including the need for states to cooperate and the emergence of international institutions. He also examines the role of power and the balance of power in international relations. The book is an important contribution to the field of international relations and is still widely read and discussed today.

Bull identified the idea of an anarchical society within which a society of states operates in spite of this anarchy. A society of states is formed when states realise that they have common interests and values and will benefit from working together. When this happens, states begin to interact and impact on each others’ decisions, so ‘they behave — at least in some measure — as parts of a whole’. This could be described as liberal realism or self interested realism. International politics exists in a stae of anarchy but states recognise that they do have some mutual interests. Adam Watson defined as 'the idea that it pays to make the system work'.

A system of states can exist without it also being a society of states. A society of states comes into existence "when a group of states, conscious of certain common interests and common values, form a society in the sense that they conceive themselves to be bound by a common set of rules in their relations with one another, and share in the working of common institutions.


Hans Morgenthau, Politics Among Nations (1948) Morgenthau is a classical realist thinker. Political man is a naturally selfish creature and will always try to dominate and have power over others. Moral considerations in global politics are less important than the national interest. Hans Morgenthau is considered one of the "founding fathers" of the realist school in the 20th century. This school of thought holds that nation-states are the main actors in international relations and that the main concern of the field is the study of power. Morgenthau emphasized the importance of "the national interest", and in Politics Among Nations he wrote that "the main signpost that helps political realism to find its way through the landscape of international politics is the concept of interest defined in terms of power." Morgenthau is sometimes referred to as a classical realist or modern realist in order to differentiate his approach from the structural realism or neo-realism associated with Kenneth Waltz. Recent scholarly assessments of Morgenthau show that his intellectual trajectory was more complicated than originally thought. His realism was infused with moral considerations -- though not always acknowledged as such -- and during the last part of his life he favored supranational control of nuclear weapons and strongly opposed the U.S. role in the Vietnam War

John Mearsheimer, The Tragedy of Great Power Politics (2001) Mearsheimer is an offensive realist thinker. He explained that conflict and competition for power between the great world powers will continue. States are trying to secure hegemony, meaning they want to dominate all other states within a region. John Mearsheimer's The Tragedy of Great Power Politics is an influential and widely-read book that provides an in-depth analysis of the international system and the dynamics of great power politics. Mearsheimer argues that great powers are driven by the desire for security and that they are willing to use force to protect their interests. He also argues that states are rational actors and that they will act in their own self-interest. He further argues that the international system is anarchic and that states must compete for power and resources in order to survive. Mearsheimer's book is an important contribution to the field of international relations and provides an insightful look at the dynamics of great power politics.

Mearsheimer is the leading proponent of offensive realism. The structural theory, unlike the classical realism of Hans Morgenthau, places the principal emphasis on security competition among great powers within the anarchy of the international system, not on the human nature of statesmen and diplomats. In contrast to another structural realist theory, the defensive realism of Kenneth Waltz, offensive realism maintains that states are not satisfied with a given amount of power but seek hegemony for security because the anarchic makeup of the international system creates strong incentives for states to seek opportunities to gain power at the expense of competitors. He also dismisses democratic peace theory, which claims that democracies never or rarely go to war with each other.



Mearsheimer summarized that view in his 2001 book The Tragedy of Great Power Politics:

Given the difficulty of determining how much power is enough for today and tomorrow, great powers recognize that the best way to ensure their security is to achieve hegemony now, thus eliminating any possibility of a challenge by another great power. Only a misguided state would pass up an opportunity to be the hegemon in the system because it thought it already had sufficient power to survive.