This is another excellent paper in Greenson's series on the metapsychology of moods. The author differentiates enthusiasm from other types of elation. Enthusiasm is defined as a passionate and idealized state of mind in which the wish to share with others is compelling. It is a temporary state dependent on the approval of others for heightened self-esteem. There is a reduction in reality testing and superego functioning. Pleasure comes from the sense of fusion with the object and from a denial of painful reality; the greater the denial, the more the enthusiasm is a pathological defense. Union with the idealized object does away with the tension between ego and superego, allowing for discharge of large amounts of id energy, mainly libidinal; this energy is unneutralized but may serve sublimation. The genetic model for enthusiasm is the nursing child who anticipates both satiation and deprivation: the memory of hunger makes the child nurse enthusiastically and with a feeling of security as long as the mother is involved pleasurably in the complementary relationship.