Drawing on the account of a clinical experience, this article is a testimony on two counts. Firstly, the author discusses the close, complex and sometimes paradoxical relations that can exist between hatred and love. It illustrates the different possible expressions of hatred: between open, undisguised hatred and veiled hatred, between hatred of the other and hatred of oneself, between necessary, even fundamental hatred, and the hatred that is present in certain extreme psychopathological situations. Secondly, by talking about his practice and his own experience in the clinical situation, the author shows how hatred acts as a force that is sometimes separating and sometimes uniting. To witness another's relationship to hatred is to be traversed by specific affects and ideational contents, as well as by the need – at times – to adopt a position in the analysis, whether in words and/or deeds. These developments lead the author to present the links between hatred, the construction of identity and the sense of existing.