ABSTRACT
The practical limitations of experiments on humans can be reduced by effort, ingenuity, and resources. The inherent limitations cannot. In the last analysis, the laboratory is not the world. The relevance of effects induced in the laboratory to phenomena observed in the world is inherently uncertain. The uncertain relevance of the cause found in an experiment to real-world variation means that experiments do not resolve the question of causal order in the real world. Doing something to the subjects and seeing what follows establishes the causal order within the experiment. Finding an effect of the manipulation does not rule out the possibility or primacy of the opposite effect. Effectiveness of treatments does not tell us what causes depression. An effective treatment may not be as effective as removing the cause. And an effective treatment may be a net deficit if it deters the search for the problem causing the depression and a solution to the problem.
