This work is based on the theory proposed by Donald W. Winnicott and aims to investigate the loss of the symbolic capacity in borderline pathology. At first it is held a discussion about the theoretical and clinical diagnostic guiding principles that sustains Winnicott s diagnostic criterium. The primitive emotional development is then investigated in order to clarify the failures that results in the establishment of borderline pathology. Then it is argued that the creation of a heavily invested false self and a damage to the space potential are defining characteristics of the borderline pathology that distinguishes it from other diseases that also originates from early environmental failures. Subsequently, we discuss the relation between potential space and symbolic capacity, it is also discussed the importance of the transitional object as the first symbol of the separation between self and non-self. In the final part of the paper we address the issue of trauma in the potential space, which results in injury to the symbolic capacity, concluding that the interference in transitionality affects the process of separating external and internal realities, which results in the impairment of the symbolic capacity of borderline patients.