Starting from an exploration of the functions of hate in the genesis of the object and the constitution of the subject, the author studies the vicissitudes of hate and love in their respective relations with loss within the object relation. After analysing this crucial stage of differentiation between the ego and what is not-ego, which takes place following the loss of a condition of narcissistic plenitude, the author studies the primary role of the projection of the experience of unpleasure and of what is bad on to the object and the hated external world. Taking these processes into account, the author goes on to explore Franco Fornari’s hypothesis that conflicts of hatred and war could be understood as attempts at a paranoid elaboration of mourning in order to cope with the depressive and paranoid anxieties that subjects and groups may experience when confronted with loss.