This article compares the phenomena of tic and slip of the tongue [lapsus] as they have been described by Maine de Biran and Victor Egger, including a possible reception of Biran’s thought by Egger. In the 20th century these phenomena will be analysed by psychoanalysis, but their first description appears in nineteenth-century French philosophy. Starting from the analysis of Biran’s tics and Egger’s slips, the extent to which the concept of habit is linked, since the nineteenth century, to a reflection on the unconscious emerges. Tic and slip of the tongue constitute, each in its own way, the place where habit exhibits its most peculiar characteristic, that of being always suspended in the dual dialectic of the voluntary and the involuntary, of the conscious and the unconscious. Maine de Biran’s habit tics underline the tendency set by habit for which voluntary and conscious actions become involuntary and unconscious, whereas Egger defines slip of the tongue as an involuntary and unconscious event that allows the birth of new habits.