The borderline personality disorder has long been perceived as a marginal phenomenon within the field of psychiatry and psychotherapy. However, in recent decades, there has been a steadily increasing interest, particularly in American research. Various new literary publications refer to the borderline phenomenon as a disease of modernity, which, according to estimates, currently represents the third largest group of mental disorders. The borderline disorder and its treatment methods are now almost exclusively explained by the contributing psychiatrists, psychologists, and psychotherapists through concrete examples. This development is attributed to the prevailing uncertainty in professional circles regarding this disorder. For a long time, it seemed that there was little understanding of what lay behind it.