All the defensive measures of the ego against the id are carried out silently and invisibly. The most we can ever do is reconstruct them in retrospect: we can never really witness them in operation. … definite indications of obsessional exaggeration suggest that it is of the nature of reaction and that it conceals a long-standing conflict. Here again, observation of the particular mode of defense does not reveal anything of the process by which it has been evolved. The transference phenomenon which we have interpreted falls into two parts, both of which have their origin in the past: a libidinal or aggressive element, which belongs to the id, and a defense mechanism, which we must attribute to the ego – in the most instructive cases, to the ego of the same infantile period in which the id impulse first arose. When the transference reactions take this form [transference of defense], we cannot count on the patient's willing cooperation, as we can when they are of the type first described [transference of libidinal impulses]. Whenever the interpretation touches on the unknown elements of the ego, its activities in the past, that ego is totally opposed to the work of analysis. Only the analysis of the ego's unconscious defense operations can enable us to reconstruct the transformations which the instincts have undergone. It [the term " defense " ] occurs for the first time in 1894 … to describe the ego's struggle against painful or unendurable ideas or affects. Were it not for the intervention of the ego or of the external forces which the ego represents, every instinct would know only one fate – gratification.