In his theory of trauma, Ferenczi points to the disbelief of adults of a child's account of an event as an actual traumatizing factor. Ferenczi also states that of all the consequences of the trauma, which include identification with the aggressor, psychic coma, departure from the possibility of dreams, and a fall to the hell of nightmares, the most important and fundamental is the lack of certainty of self. The disbelief of the adults destroys the certainty of what is perceived and experienced; it has the power of annihilating the child's belief in his own perceptions, his trust in his own senses. The loss of certainty of self appears to be a common characteristic in patients with distinct psychic dynamics. We will analyze the loss of certainty of self in cases of patients of the NEPECC (Núcleo de Estudos em Psicanálise e Clínica da Contemporaneidade) [Center of Studies in Psychoanalysis and Contemporarity Clinic] at the Federal University of Rio de Janeiro.