This paper addresses the movement toward dedifferentiation of subject and object in the psyche as essential for a full understanding of the strange power of sexuality, and orgasm in particular. The movement toward union is presented as a fundamental, erotically infused softening of difference and boundary between self and other. This tendency toward dedifferentiation is always in dialectic with a movement toward recognition of difference, otherness, and separateness. I suggest that sexuality and orgasm can serve a unique function of allowing for the gathering of excesses of all kinds and dissolving them into an experience of expansion and dedifferentiation. I present my work with a patient for whom exploration of erotic phantasies of merger and union were essential for her recovery from depression and toward creative expansion. The case allows for an inquiry into the importance of phantasies of erotic dedifferentiation for psychic growth.