In the paper he argued, based on clinical material, that his borderline patients were extraordinarily attuned to the emotions of others, to the degree that they often felt things that other people were unaware they themselves were feeling. They were often able to intuit “very private impulses and judgments in other people.” Yet it was not empathy itself which earned these patients a borderline diagnosis.

Rather, it was their weak sense of self and ego organization, which left them at the mercy of their emotions with very little ability to reflect upon them or bring reason to bear upon their judgments of others. While at times the borderline is uncannily correct about other people’s feelings or the “emotional atmosphere” in the room, at other times they are deeply, profoundly wrong—especially when they fail to differentiate between their own feelings and those of others, or when they bring a rigid, caricatured set of emotional responses to everyday social interaction.

Upon delving more deeply into patients’ life histories, Krohn discovered that many of these patients were deeply sensitive, empathetic children whose abilities had been exploited and manipulated by parents with severe emotional difficulties. These parents often made the borderline child into a source of constant gratification of their emotional (and at times sexual) needs, and abandoned or violently turned against the child if they refused to be used in this way. As a result, the child never developed a firm sense of self independent of others and became a hypervigilant scanner of the emotions of people around them both so they could fuse with them (and thereby maintain relationship) or violently reject them (thereby protect themselves from abuse and further exploitation).

It's important to stress that the borderline’s characteristic practice of “splitting” others into all-good or all-bad objects is a repetition of behaviors they learned from parents or other caregivers who did this to them repeatedly as they grew up. In other words, borderline personality disorder is a kind of malformation of a person’s empathic capacity. Empathy is one tool among many that healthy people use to make decisions and grow relationships with others. The borderline, however, is enslaved by empathy, which leads them at times to radically disregard it in a bid to protect themselves by abusing and lashing out at others. In those moments, a borderline person finds it very difficult to imagine or feel what those around them may be feeling. This is why healing from borderline personality disorder is all about learning to use empathy in more centered, balanced way. Rather that the extremes of being completely overwhelmed by what others are feeling and then completely cutting off awareness of what others are feeling, the patient must learn how to observe others’ emotions while remaining their own person—with their own feelings and thoughts, especially when they are feeling strong emotions.

This psychological separation from other people is a coming into integrity. It helps the patient feel like they exist in the world as separate individuals, not just as extensions of other people. It helps them learn that healthy relationships allow both people to be who they are, so that no one is burdened with having to manage the emotions of anyone else.

And most importantly, it helps the borderline take responsibility for themselves—rather than feeling impossibly responsible for others while blaming those others for things which are their own responsibility.