Feuerbach · Friedrich Engels
I.
The chief lack of all materialistic philosophy up to the present, including that of Feuerbach, is that the thing, the reality, sensation is only conceived of under the form of the object which is presented to the eye, but not as human sense-activity, "praxis," not subjectively. It therefore came about that the active side in opposition to materialism was developed from idealism, but only abstractly; this was natural, since idealism does not recognize real tangible facts as such. Feuerbach is willing, it is true, to distinguish objects of sensation from objects existing in thought, but he conceives of human activity itself not as objective activity. He, therefore, in the "Wesen des Christenthums," regards only theoretical activity as generally human, while the "praxis" is conceived and fixed only in its disgusting form. The question if objective truth is possible to human thought is not a theoretical but a practical question. In practice man must prove the truth, that is the reality and force in his actual thoughts. The dispute as to the reality or non-reality of thought which separates itself, "the praxis," is a purely scholastic question. The materialistic doctrine that men are the products of conditions and education, different men therefore the products of other conditions and changed education, forgets that circumstances may be altered by men and that the educator has himself to be educated. It necessarily happens therefore that society is divided into two parts, of which one is elevated above society (Robert Owen for example). The occurrence simultaneously of a change in conditions and human activity can only be comprehended and rationally understood as a revolutionary fact.
Text from Project Gutenberg, public domain in the United States.