In this paper I explore the systematic place and function of the expression "Scheinlehre" (Doctrine of the Appearance) in Fichte's philosophy. Given that this expression is to be found for the first time in the Doctrine of Knowledge of 1804, where Fichte identifies it with "Erscheinungslehre" (Doctrine of the phenomenon) and "Phänomenologie" (Phenomenology), I focus on the version of 1804 of Fichte's philosophy. The thesis of my paper is that the Doctrine of Knowledge of 1804 plays with the idea of conceiving the real appearance of the absolute (ideal) unity of reason. This thesis encompasses three questions: the motif of the One, the motif of the phenomenon and the motif of the genetic construction of the problem (the truth).