In scholarship on the history of philosophy, it is widely assumed that Charles Fourier was a utopian socialist who could not have exerted a significant influence on the development of Karl Marx's thought. Indeed, both Marx and Engels seem to have advanced this view. In contrast, I argue that in 1844 when Marx was developing his anthropology and social critique, he relied upon Fourier's thought to supply a key assumption. After establishing this connection, I explain why Marx's tacit reliance on (...) Fourier creates a problematic undercurrent in his thought. (shrink)