Realism claims to be the oldest body of theory in the study of international relations. Essentially concerned with the study of war and peace between nations, realism sees a world that is inevitably and permanently divided intonation-states, controlled by rational governments interested in protecting their security. Realists have divided on how they believe most governments naturally attempt to do this: so-called classical realists argue that governments attempt to increase their power as much as possible (the more powerful a state is, the more it can control its own destiny), while so-called neorealists argue that states can increase their security without necessarily being power-hungry (the safer a state is, the more it can control its own destiny).
As with all academic theories, there is a surprising amount of variation among the theories and assumptions put forward by both alleged and self-identified realist scholars. Even the number of shared principles among all realists seems to be in flux: for example, Hans Morgenthau identified six principles, but according to Jack Donnelly, Robert Gilpin finds only three and Randall Schweller actually lists seven. Most college-level surveys hit upon five, and I will do the same here.
The fundamental assumption of all realist theory is that the international system (that is, the collection of independent nation-states that make up global politics) is anarchic: there is no overarching power or government or law that actually calls the shots. Nations make up their own rules as they go, and are in charge of their own affairs. Realists attribute this state of affairs to the 1648 Treaty of Westphalia, although this is debatable.
That anarchic system, moreover, is composed solely of nation-states, and more specifically of state governments. Other actors, like international organizations and multinational corporations, are assumed to play minor and insignificant roles in global politics.
Third, all of these states are rational and are driven by the goal of survival. To survive — and to achieve safety, or “national security” — is the first objective of all countries. Usually, countries pursue this security, and exercise their power, through military means, but sometimes they do so through economic power as well.
Finally, realists argue that there is no morality in international politics. In other words, states cannot allow themselves to be guided by any sense of ethics higher than the drive to survive, and they must assume that other states will be doing the same. Hans Morgenthau also claimed that attempting to add morality into politics would lead to senseless ideological wars.
Strengths and Weaknesses
Its easy and basic applicability to the most traditional of international activities — power politics and war — can make realism very appealing, especially to students looking for a relatively easy-to-apply theory. Moreover, realism is best when engaging with powerful states (especially superpowers like the United States and the Soviet Union) on their own terms, seeing the world from their perspective and focusing on the conflicts and crises that tended to occupy the attention of most of their diplomats and security analysts during the Cold War.
Realism has many gaps, however. There is virtually no attention paid to how the internal makeup of different states leads them to have different foreign policies (a communist dictatorship and a liberal democracy are assumed to have effectively the same international behaviour, for instance). Realists also cannot explain the decline of states in the face of international organizations and multinational corporations in the economic sphere. Perhaps most importantly, realism has, on the face of it, little to say about the current “war on terror,” which involves states on one side but non-state terrorist groups on the other. (Some realists might counter that the “war on terrorism” is simply an ideological cover and that the real conflicts continue to be between the U.S. and other governments, like those of Iran and formerly of Iraq and Afghanistan.)
Most realists today argue that their discipline began with the work of Ancient Greek historian Thucydides (The Peloponnesian War), Italian Renaissance politician Niccolo Machiavelli (The Prince), and less often Chinese strategist Sun Tzu (The Art of War) and English political theorist Thomas Hobbes (Leviathan). Whether these writers were genuinely realists or modern-day scholars are simply engaged in selective historical cherry-picking is debatable.
Either way, the modern academic field of realism was founded in the 20th century by German-American scholar Hans J. Morgenthau (Politics Among Nations). A second wave of realist work was initiated by Kenneth Waltz (Man, the State, and War, and Theory of International Politics), and is currently known as neorealism. Most realists today actually identify with the neorealist camp, although they demonstrate a wide variety of different assumptions and beliefs about global politics. Such scholars include John Mearsheimer (The Tragedy of Great Power Politics), Robert Jervis (Perception and Misperception in International Politics), Stephen Walt (The Israel Lobby and U.S. Foreign Policy), and Robert Gilpin (The Political Economy of International Relations).
Another body of theory, the so-called English School of International Relations, draws heavily upon realist theory, and some of its members, like Hedley Bull (The Anarchical Society), actually identify as realists. At the undergraduate level the English School can usually be described as realist, although there actually are significant (if nuanced) differences between the two theories.