74 CHAPTER THREE ■ InternatIonal relatIons theorIes
deduction of hypotheses from assumptions and a testing of the hypotheses as more and
more data are collected in the empirical world, we often must revise or adjust theories.
This pro cess is, in part, a creative exercise, in which we must be tolerant of ambiguity,
concerned about probabilities, and distrustful of absolutes.
International relations (IR) theories come in vari ous forms. In this chapter, we intro-
duce four general theories, or theoretical perspectives, in the study of international
relations: realism (and neorealism), liberalism (and neoliberal institutionalism), radi-
calism (in this case, Marxism), and social constructivism. The attempt to explain such
impor tant and complex things as war, peace, oppression, economic development, and
crisis remains ambitious; explanations require constant testing and revision. Before we
examine these theories more closely, we apply three levels of analy sis— a tool IR theo-
rists use to manage the bewildering complexity of the empirical world—to the 2003 U.S.
and co ali tion invasion of Iraq.
theory and the levels of analy sis
The United States and its co ali tion partners invaded Iraq in 2003. Understanding why
and when the invasion happened may prove critical in challenging con temporary IR
theory— and in preventing future wars. What then is our best explanation of the
invasion? We can or ga nize the list of pos si ble explanations according to three levels of
analy sis (see Figure 3.1). Dividing the analy sis of international politics into levels
helps orient our questions and suggests the appropriate type of evidence to explore. Pay-
ing attention to levels of analy sis helps us make logical deductions and enables us to
explore all categories of explanation.
A categorization first used by Kenneth Waltz and later amplified by J. David Singer
offers three diff er ent sources of explanations. If the individual level is the focus, then
the personality, perceptions, choices, and activities of individual decision makers (e.g.,
Saddam Hussein and George W. Bush) and individual participants (e.g., Defense Sec-
retary Donald Rumsfeld and Saddam’s sons) provide the explanation. If the state level,
or domestic factors, is the focus, then the explanation is derived from characteristics of
the state: the type of government (e.g., demo cratic or authoritarian), the type of eco-
nomic system (e.g., cap i tal ist or socialist), interest groups within the country, or even
the national interest. If the international system level is the focus, then the explanation
rests with the characteristics of that system (such as the distribution of “power”) or
with international and regional organ izations and their relative strengths and weak-
nesses.^2
Box 3.1 on p. 76 categorizes pos si ble explanations for the Iraq War according
to these three levels of analy sis. Of course, explanations from all three levels prob ably
contributed to the United States’ decision to invade Iraq in 2003. The purpose of theory