The Borderline Personality Disorder (BPD) diagnosis was originally introduced in DSM-III as a new category separated from the other “borderline” condition of schizotypal personality disorder. Until this point, the “borderline” concept had served as a metaphor for conditions on the border to schizophrenia and mood disorders. The “borderline” concept was, thus far, a well-established severity indicator for any marked character disorder, which was now turned into a distinct category or syndrome including diverse symptoms such as mood and identity problems, self-mutilating behavior, feelings of emptiness, and episodic aggression. In a 2016 interview, “the father” of BPD, John Gunderson, offered a candid reflection about the initial conception (and perhaps vagueness) of the BPD diagnosis: