Is Religion the Opium of the Masses?

Though others before Karl Marx had promoted the idea, he made it famous: “Religion is the sigh of the oppressed creature, the heart of a heartless world, the soul of soulless conditions. It is the opium of the people.” What does the religion-as-opium argument imply? Atheists allege that just as opium intoxicates people with illusory feelings of well-being without offering any real relief, so does religion. Only when people shed the false hopes offered by religion will they strive for actual well-being.