In Chapter Three of Neorealism and its Critics, edited by Robert O. Keohane, Kenneth N. Waltz explores reductionist and systemic approaches to international relations. Waltz writes that both types of theories deal with every event which occurs in international relations, from the smallest and most local to the largest and most global. Therefore, what makes a theory reductionist or systemic is not the events the theory deals with, but the way the theory deals with those events. As we read,
Reductionist theories explain international outcomes through elements and combinations of elements located at national or subnational levels. . . . A systems theory of international politics deals with the forces that are in play at the international, and not at the national, level. . . . (47; 60).
It is the view of Waltz that reductionist theories are not effective in dealing with international relations. He believes that only systems theories are capable of taking a broad enough perspective to effectively analyze and understand all the complex activities of international relations.
Waltz says that reductionist theories look at the attributes of individual nations, for example, and then try to predict the international outcome which will occur when those nations interact. He argues that this will produce unreliable predictions because "From attributes one cannot predict outcomes if outcomes depend on the situations of the actors as well as on their attributes" (47-48).
In another example, Waltz argues against such reductionist theorists as Kissinger and Morgenthau who put much importance on the intentions of states and the effect those intentions have on international relations. Waltz writes that
In order to take [such reductionists] seriously, we would have to believe that no important causes intervene between the aims and actions of states and the results their actions produce. In the history of international relations, however, r...