This paper presents a “neo-classical realist” understanding of the sources of states’ foreign policies. The
argument is “classical realist” in the sense that it agrees with the most important classical realists of the twentieth
century—Hans Morgenthau, Reinhold Niebuhr, Henry Kissinger, and Raymond Aron—that power and ideological
variables together are the key determinants of states’ core security policies. The argument is “neo” in the sense that
it draws on sources that are more methodologically and analytically rigorous in terms of both theory development
and testing than are the discussions found in traditional classical realist writings.
The paper’s analysis consists of three principal sections. The first establishes the importance of ideological
variables to states’ core security policies in the writings of the classical realists listed above. The second presents
both a detailed causal logic that explains how ideologies shape international relations and evidence from the great
powers’ foreign policies over the last 215 years that supports these claims. I also demonstrate in this section how
power variables combine with ideologies to shape leaders’ choices. Sometimes power supplements the effects of
ideologies on outcomes; sometimes the two sets of variables work at cross purposes. The third section provides
some policy recommendations generated by the analysis.
Classical Realism and the Importance of Ideological Consensus
All realists, both classical and neo, agree that power variables are critical determinants of the most
important outcomes in international relations. Power can be both a key source of international conflict through the
workings of the security dilemma, as well as a potent deterrent against aggression and thus an important cause of
international peace.
A critical distinction, however, between classical and neo-realists is that the former believe that ideological
variables are at least as important as power in determining states’ foreign policies. To neo-realists, ideologies have
little or no effect in international relations compared to the impact of power. As Kenneth Waltz puts it, to neo-
realists "considerations of power dominate considerations of ideology."
Classical realists take a very different position on this subject. A critical, though often overlooked, theme
in the writings of Morgenthau, Niebuhr, Kissinger, and Aron is that ideological agreement (or lack thereof) among
states’ leaders works together—and is often prior to—power variables in determining politicians’ most important
international choices. To these scholars, agreement among countries’ policymakers on core domestic-ideological
objectives, such as the nature of political and economic institutions and other core social values, creates powerful
1
Kenneth N. Waltz, "Realist Thought, Neorealist Theory," Journal of International Affairs 44, no. 1
(Spring/Summer 1990): 31.
2
Convention