How valuable are psychotherapy experiments? The idiographic problem

The idiographic problem is said to arise because psychotherapy experiments study groups of subjects, whereas the clinician wants useful etiological or treatment information concerning a single, unique client. One response is to place little value on psychotherapy experiments and to argue for nonexperimental methods for obtaining clinical knowledge. It is argued here that these alternative methods are defective and that the idiographic problem can be solved without renouncing experimental methods.