Causal relations in field research as a basis for practical control

The utility of causal relations in field research for practical control is critically examined. It is argued that generalizations involving hypothetical intervention or change, formulated in terms of the parameters of causal regression functions for natural variation, are incompatible with the formal selection requirements for use of these functions. Practical results may thus deviate markedly from those predicted by the functions. Consequently, the causal relations commonly measured in field research within psychology and related disciplines cannot be used in any strict sense for the purpose of practical control. This conclusion, however, applies to generalizations involving intervention which are based on natural variation, not necessarily to those based on manipulated variation. The account demonstrates the importance of adopting a concept of causality which makes a clear distinction between causal measurements, on the one hand, and generalizations from such results, on the other.