If more than the cogitob were the ground of our pure rational cognition of thinking beings in general; if we also made use of observations about the play of our thoughts and the natural laws of the thinking self created from them: then an empirical psychology would arise, which would be a species of the physiology of inner sense, which would perhaps explain the appearances of inner sense, but could never serve to reveal such properties as do not belong to possible experience at all (as properties of the simple), nor could it serve to teach apodictically about thinking beings in general something touching on their nature; thus it would be no rational psychology.