"What is learned?"--A theoretical blind alley.

The pursuit of knowledge frequently has been hampered by misdirection. Questions lacking any possibility of being answered experimentally are often considered to be empirically meaningful. In many instances this inherent lack of meaning is so well hidden that much time and effort is wasted on attempted answers. The history of psychology has contained many such cases of "meaningless questions"; the search for the basic elements of consciousness and the attempt to estimate whether intelligence is determined by hereditary or environmental variables are but two of the more outstanding examples of such unanswerable questions. The history of these questions appears to follow a common course of development. Initially the question provokes much interest and seemingly opposed speculations are offered as possible answers. Then the question is subjected to experimental attack. This usually intensifies the theoretical differences because much bickering is instigated about the adequacy of the experimental design as well as the correct interpretation of the experimental data. The result is that agreement is never attained. Gradually the interest in the question subsides and successive generations of scientists learn to avoid the question because they intuitively recognize the futility of pursuing it. Then,