" The main defect of all hitherto-existing materialism — that of Feuerbach included — is that the Object [der Gegenstand], actuality, sensuousness, are conceived only in the form of the object [Objekts], or of contemplation [Anschauung], but not as human sensuous activity, practice [Praxis], not subjectively. Hence it happened that the active side, in opposition to materialism, was developed by idealism — but only abstractly, since, of course, idealism does not know real, sensuous activity as such. Feuerbach wants sensuous objects [Objekte], differentiated from thought-objects, but he does not conceive human activity itself as objective [gegenständliche] activity. "
― Karl Marx , Eleven Theses on Feuerbach