This paper focuses on the basic features of Fichte's doctrine of perception as laid down in his Thatsachen des Bewußtseyns aus dem ws 1811/12. Special attention is given to Fichte's analysis of external perception and of the role played by extension (Ausdehnung) as an essential component of it. In Fichte's view, extension is characterized by, among other things, the fact that it presupposes some kind of freedom. This is closely related to Fichte's view that freedom is not something whose representation is just added to other representations. According to him, it is the reverse: freedom (viz. the representation of freedom) is already entailed in many other representations - it is a determining, if tacit (or, as he puts it, hidden and invisible) factor that decisively shapes many other representations viz. their content.