Proof that resistive behavior in psychotherapy is due to mobilization of the patient's defenses requires elimination of alternative

explanations for the resistance. Careful scrutiny of how interpretations are arrived at and used gives a clue to how this discrimination can be made. The therapist uses probing remarks, which resemble trial interpretations, and he keeps to a minimum all conditions provocative or permissive of nondefensive resistance. Free association is a procedure that is especially useful in determining whether resistance has a defensive origin. What we call resistance differs with different kinds of therapy. But whatever the therapy, the therapist must be careful to control the conditions of therapy and must be well informed about the patient and the circumstances of his behavior if he is to spare himself the labor of developing incorrect defense interpretations.