Ludwig Feuerbach was a contemporary of Marx who wrote philosophical critiques of religion and one of Marx's inspirations for alienation.  The "Theses on Feuerbach" were written in spring 1845.  Marx makes several important points here
The important question of the relationship of theory and practice emerges here.  Here's how one dictionary of Marxism puts it:
Theory and Practice are the ideal and material aspects of human activity. Theory reflects and organises practice; practice manifests and enriches theory. The separation of theory and practice, which has its origins in the rupture of society into classes, means speculation in theory and unconscious activity in practice.
This resonates with a question we will encounter in the work of Max Weber on the relationship between politics and science and also with Karl Mannheim's consideration of the question of the possibility of a "scientific politics" in Ideology and Utopia (pp. 194ff in RST).
Conventional materialism has ideas "growing out of" material conditions.  And practice can be the externalization of ideas.  But this pictures action strictly as product of environment.  Where does that environment come from?