How is self-deception possible? There are many foundational questions involved in understanding our defences. Are these manoeuvres unconscious processes to which we fall prey, as psychoanalytic metapsychology suggests? Or are they the product of a conscious and motivated strategy initiated by the individual? I argue for the latter. The concept of “unconscious defence” lacks explanatory power as it initiates an endless cycle of defence mechanisms. Alternatively, focus is directed towards consciousness and the pre-reflective moment when the ego evades addressing troubling content of consciousness. Existential philosophers such as Sartre and Fingarette (1969) are used as stepping stones in making this “Copernican” shift in perspective, and core affective processes are introduced as the organismic centre of rotation behind our defences. Core affective processes play an important role in the toning of our emotions and moods, and I argue that they also play a leading role in the activation of our defences. A case study documents the mechanisms. Finally, ethical issues raised by self-deception in psychological practice are touched upon. Should the truth always be revealed, or should psychologists occasionally engage in cost-benefit analysis?