The author questions whether Kernberg's suggestion that the interaction between splitting and other defence mechanisms - such as primitive idealization, omnipotence, devaluation and denial [disavowal] - gives an adequate psychodynamic explanation of borderline personality structures. The author shows that the assumption of a splitting mechanism provokes contradictions and that primitive idealization, omnipotence, devaluation and disavowal cannot be seen as genuine defence mechanisms. He argues that primitive idealization is a type of reaction formation and that the omnipotence of these patients can be put down to identification with the idealized ego-functions of their objects. He also maintains that the clinical phenomena can be understood as the outcome of a combination of an “equiparant” and “disequiparant” isolation, displacement, projection and primitive idealization, making the concept of splitting as an explanatory device superfluous.