As unstintingly irreligious as he was, Karl Marx was not an atheist. He was a staunch opponent of supernatural belief, yet neither did he embrace agnosticism as the position of claiming no answer to the question whether or not God exists. Rather, Marx argued that it was incoherent and pointless even to pose that very question. His irreligion is best understood not primarily as an ontological stance on the existence or nonexistence of God, but rather as part and parcel of (...) a philosophical worldview radically committed to sweeping such questions aside, to centering the human perspective ontologically and epistemologically, to overthrowing “all relations in which man is a debased, enslaved, forsaken, despicable being,” and to taking as its core principle that “man is the highest being for man.” A “religious worldview” for Marx includes not only the plainly divine, but any perspective that subordinates the value of human beings to a superior entity, operating externally to human beings and imperviously to their influence. I begin by explaining the relationship between Marx's historical materialism and his position on the existence of God. It may seem obvious how irreligion would follow from a philosophical materialist stance. I show that Marx's historical materialist irreligion, however, warrants a closer and more nuanced assessment than we might at first realize. I go on to discuss why Marx's historical materialism leads him to regard questions about the existence of God as fundamentally misguided. I then unpack the meanings of Marx's infamous statement that religion is “the opium of the people.” I conclude with a discussion of Marx's pronouncement that “the criticism of religion ends with the teaching that man is the highest being for man,” a teaching that separates mere atheism from radical irreligion. (shrink)