This paper suggests writing the history of psychoanalysis by focusing on the manifold ways in which its practitioners may relate to the boundaries dividing it from its neighbouring professions. This approach is illustrated by two loosely interrelated examples: the 1950s debate among leading US psychoanalysts on whether borderline patients can be analysed, and the 1990s responses of psychoanalysts to psychopharmacological treatments of schizophrenia. A close reading of psychoanalysts' journal publications reveals in each instance multiplicity (of voices), instability (of boundaries), duality (of defence and dialogue) and simultaneity (of internal and external addressees). At the same time, a common rhetorical stance emerged in each period, serving as a shared discursive frame while allowing a plurality of boundary relations.