Case Studies and Theory Development in the Social Sciences - Alexander L. George [97]
Z–→C–→E
A third possibility is that C can be defined as lacking causal depth if a third variable Z would have brought about E even in the absence of C. In this instance, it does not matter whether or not Z is related to C. In other words, Z has greater causal depth because it appears to be necessary and sufficient for E, and Z may act through C or through some other variable X. In contrast to the example of causal priority, C is not in this instance a necessary condition for E.382
Thus, the appearance of congruence, especially when only one or primarily one theory is considered, cannot support an inference of causality, nor does the lack of congruence deny a possible causal role. Moreover, even if a congruence test suggests that a variable played a causal role in a given case, this does not mean that this theory proposes causal factors that are necessary, sufficient, or causal in any sense in other cases where contextual and conjunctive variables are different.
These problems of spuriousness, causal priority, and causal depth underscore that congruence tests by themselves may be inconclusive when several competing theories are involved. In such circumstances, for causal relations short of necessity or sufficiency, congruence tests are very difficult unless all the effects of the theories in question have been established with precision and confidence through previous testing. The problem is that alternative theories may focus on the same independent variables but point to different causal mechanisms that relate these variables to the observed outcome. The theories compete in logic, but may or may not make different predictions on the outcome. Theories may also be complementary, addressing different variables without contradicting one another logically. Such complementary theories may either reinforce or counteract one another’s predicted effects.
A real-world example, drawn from Andrew Bennett’s research on the rise and fall of Soviet military interventionism in the Third World in the 1970s and 1980s, illustrates these issues. The “Reagan Doctrine” and “Soviet economic stringency” explanations for Soviet retrenchment in the 1980s are complementary, and they both pointed toward an increased likelihood of Soviet retrenchment. Retrenchment occurred, but the congruence method alone cannot tell us if both explanations were important factors, if only one was primarily responsible for the outcome, or if neither was causal and the result was driven by other variables.383
Now consider the problem of competing explanations. A competitor to the Reagan Doctrine theory is the “hard-line reactive theory,” which holds that the Reagan Doctrine aid, rather than speeding up Soviet retrenchment, galvanized a hard-line coalition in the Soviet Union and delayed the retrenchment in Soviet foreign policy.384 These competing views on the effects of the Reagan Doctrine complement the economic stringency view and are consistent with the outcome of retrenchment. The difference is that the Reagan Doctrine theory suggests that U.S. aid to Afghan rebels, in addition to Soviet economic constraints, led to the Soviet withdrawal from Afghanistan; the hard-line theory could suggest that Soviet economic constraints, despite the delays and hedging caused by the hard-line coalition, caused the Soviet withdrawal. These competing versions can be tested for congruence with the timing, nature, and completeness of the Soviet withdrawal.
This example also illustrates why it is important not to summarily dismiss explanations that seem inconsistent with the outcome. In this case, trends in Soviet forces for power projection appeared to be inconsistent with the Soviet retrenchment, as these forces actually grew through much of the 1980s. However, the strengthening of these forces might help explain why Soviet retrenchment did not take place