Fechner remains virtually unknown for his psychological research on the unconscious. However, he was one of the most prominent theorists of unconscious cognition of the 19th century, in the context of the rise of scientific investigations on the unconscious in German psychology. In line with the models previously developed by Leibniz and Herbart, Fechner proposes an explanative system of unconscious phenomena based on a modular conception of the mind and on the idea of a functional dissociation between representational and attentional (...) activity. For Fechner, the unconscious is a state of consciousness resulting from the isolation of representational activity from the rest of psychical life. Unconscious mental phenomena are unattended mental states that behave autonomously while remaining able to act on consciousness. This paper aims to revisit Fechner’s contribution to the history of the unconscious, but also the theoretical significance of the Fechnerian unconscious vis-à-vis current research on the cognitive unconscious. (shrink)