Karl Marx and Sigmund Freud were huge proponents of atheism in the early part of the Modern Era. Karl Marx spoke of religion as the “opium of the people.” He alleged that the need for religion derived from socioeconomic problems and if these problems were alleviated religion would no longer be a need of the people. His proposal, as most know, created communism as the solution. He proposed that a class-less society would fix the problem and create a utopia. History records a tragic bloody result of his philosophy. 
Freud on the other hand decried religion as being a result of a psychological need to project one’s childhood father relationship to a God being as an adult. In contrast, Freud had a horrible experience with his own father and yet he never developed any philosophy concerning a psychological reason for his denial of God.
Both Marx and Freud agreed that humanity had a deep desire for God. Marx linked it to economic injustice and thought that government leaders could enact the change to end the need for God. Freud thought that we would evolve past our need for God as we matured as humans and that we would see God is dead and we have killed him by rising above such childish fantasies.
However, here we are in the year 2008 and most of the planet still seeks to fill their deepest need for God and many seek to fill that need by various world religions. Christianity has a unique claim that God came down to earth as a man, the Son of God, and paid the debt of sin for us so that the way to Him is Christ and not by any penance, works, religions, mantras, rituals etc. He is the answer to our deepest need. He appeared in history, had a lineage, in a time and place that can all be verified. Even these men who are so famous for their denial of Him acknowledged the need of humanity to know Him. I don’t think there are valid needs without valid fulfillments. If you are hungry you can eat. If you are thirsty you can drink. If you are tired you can sleep. If you desire to fill your soul you can do that too, with the only One who can satisfy. There are drinks that won’t quench thirst and there are foods that won’t satisfy hunger, likewise there are religions that won’t meet the needs of the soul and there is Christ who can and will. The awesome think about finding Christ is that you can still enjoy the desire and have that desire filled at the same time. It’s as if you are drinking from the best water imaginable that isn’t to quench your natural thirst, but the thirst of your soul. Jesus said of Himself that He is that living water.
