The nervous system is operationally closed. It operates only in contact to itself. This astonishing claim has been made by Heinz von Foerster, one of the founders of radical constructivism. This work explores the consequences of his claim in the context of linear signal theory, embodiment and the creation of artificial artifacts. In linear signal theory all transfer functions can be directly associated with the neural activity where also the environment is described by neural activity. This means that the environment is no objective entity but is described in terms of internal activity. We construct the worlds in our heads. The phenomenon of embodiment is interpreted here from the perspective of the nervous system, thus from the inner perspective. To identify inside and outside an organism must learn to identify the disturbances which are only in the environment. This can be done by anticipatory learning. Thus, embodiment is a process which emerges from the anticipation of disturbances. If one wants to design artifacts in the context of constructivism one has to obey that only quantity (activity) plays a role but no interpretation of activity. In addition one has to design an agent which performs input control and not output control.