 In the following statement, Cook (1983) refers to the well-known educational researcher Cronbach about multivariate causal interdependency and validity, and the need for understanding the complexity of the situation being researched.Lawful statements of causation require full knowledge of this system of variables so that total prediction of the outcome can be achieved.From his belief in the systemic organization of causal connections and the utility of causal explanations of this type, Cronbach questions whether the experimentalists' isolation and manipulation of a small set of specific causal agents is sensitive to the real nature of causal agency, which depends on complex patterns of influence between multiple events and also involves characteristics of respondents, settings and times (p.78).