The demise of stimulus-response behaviorism has brought radical changes in the way psychologists conceptualize classical Pavlovian conditioning, as described by Rescorla (1988). The new emphasis on learned expectations sheds light on Freud's 1926 theory of intrapsychic conflict which explains neurotic anxiety by the same principles that account for realistic anxiety. Learned expectations also figure prominently in the recent writings of a number of psychoanalytic theorists. This paper uses these principles to explain "successful defense," which is customarily defined as the activation of defense in the absence of conscious anxiety. These same principles elucidate an important difference between the therapeutic mechanisms of supportive versus expressive psychotherapy. This distinction parallels the difference between conditioned inhibition versus extinction in Pavlovian conditioning.