Hopper's portrayal of the fourth basic assumption of “Incohesion: Aggregation/Massification” has two components: (1) a revision of Turquet's theory of BA Oneness to incorporate the polarity of aggregation and massification stemming from annihilation anxiety; and (2) a conception of the “difficult patient” as having an “encapsulated psychosis.” Hopper's theory of the “encapsulated psychosis” offers an important but incomplete perspective in explaining borderline and narcissistic pathology, as well as psychological trauma. In this response to Hopper, I suggest that the fourth “assumption” is in fact a still more primitive state of boundary opening and closing. I also see a need to differentiate trauma as such from borderline pathology, and further hold that the relationship between Hopper's “British Independent” theory and trauma theories based on dissociation needs to be clarified.