(Accepted for publication 18 December 2013)

In this single case study, I will address the question of how incestuous sexual abuse causes doubt of three distinct types: (1) honest doubt that is essential to the pursuit of knowledge; (2) inherent doubt that can result from a trauma that leaves the victim's mind fragmented and confused; and (3) the sadistic imposition of doubt intended to deceive, disorient and attack unbearable knowledge in the victim or another person familiar with the abuse (in this case, the analyst and the victim's later victims). During the course of my psychoanalysis of a paedophile, it became clear that this third form of doubt played an integral role in the patient's sexual abuse of children, a role I will link to the nature and function of paedophilia and to the experience of working psychoanalytically with a paedophile.