In this video, I describe the assumptions and logic of structural realist theory in more detail.

Realism has its roots in ideas expressed by Thuycidides, Machiavelli, and Hobbes, but contemporary realist theory was first expressed by Kenneth Waltz in his book Man, the State, and War. Today, John Mearsheimer and Stephen Walt are the most prominent scholars of realism, and I draw extensively from Mearsheimer’s work for this lecture.

Structural realism makes several key assumptions about the international system.

• First, realists argue that state system is anarchic.  There is no global power that can keep the peace or resolve disputes between states.
• Second, uncertainty.  States can never be sure about other states’ intentions both because states may try to misrepresent their actions but also because intentions change over time.
• Third, realists assume survival is the main goal of all states.  They acknowledge states may have other interests, but survival will always take precedence because without sovereignty, states cannot pursue those other interests.
• Finally, realists argue states are rational actors.  They behave strategically, meaning they base their decisions on a cost-benefit analysis of their own capabilities and their expectations about other states’ actions.

Based on these assumptions, realists argue that states generally behave the same way.  There are no “peaceful states” or “warlike states” – all states have similar motivations. All states seek to ensure their own survival and can only rely on themselves to do so.  States always put their self-interest first.  This means that states all seek to maximize their power relative to other states.  International politics is essentially a zero-sum game – there are no win-win situations.  What matters in all interactions in the international system is that your state wins more (or loses less) than other states. 

As noted, power is fundamental to realists’ conception of international relations.  And they tend to focus on a particular definition of power – military power.  While realists argue that the size of a country and their economy are important, they argue these factors are important because they allow a country to have a stronger military.  Ultimately, it is a country’s ability to defend its borders that determine its survival, and that requires a strong military.  Other forms of power (like cultural influence) don’t matter in this context.

I’d like to end by discussing two core concepts in and conclusions of realist theory.  The first is the security dilemma.  This is the idea that the actions a state takes to increase its security will decrease the security of other states.  This is a dilemma because those other states will then take steps to boost their security, which threatens the original state.  The easiest way to think about this is an arms race.  The United States builds a nuclear weapon to enhance its security, which threatens the Soviet Union.  The Soviet Union thus builds a weapon, which threatens the United States and inspires them to build more weapons.  This continues back and forth until both countries have enough weapons to destroy the world.

The second big concept is the balance of power.  This is the idea that when one state grows very powerful, other states will work together to challenge that state.  Alliances are possible under realism, but this cooperation is always temporary.  As Mearsheimer says in The Tragedy of Great Power Politics, “self help does not preclude states from forming alliances.  But alliances are only temporary marriages of convenience…” (p. 33).  When the relative power of states changes, their interest in cooperation will change.  The nature of the international system – whether it is bipolar (with two major powers) or multipolar (with several major powers) is thus a product of this balancing. 

Finally, I would note that not all realists agree with everything I just outlined.  Structural realism is also called offensive realism, since it assumes states always have an offensive intent.  Defensive realists argue that states seek to maximize their security, not their power, and so it is possible to resolve the security dilemma.  More on that in another lecture.