The Death of God

"Whither is God?" he cried. "I will tell you. We have killed him—you and I! All of us are his murderers! But how did we do this? How could we drink up the sea? Who gave us the sponge to wipe away the entire horizon? What were we doing when we unchained this earth from its sun? Whither is it moving now? Whither are we moving? Away from all suns? Are we not plunging continually? And backward, sideward, forward, in all directions? Is there still any up or down? Are we not straying as through an infinite nothing? Do we not feel the breath of empty space? Has it not become colder? Is not night continually closing in on us? Do we not need to light lanterns in the morning? Do we not hear nothing as yet of the noise of the gravediggers who are burying God? Do we smell nothing as yet of the divine decomposition?—Gods, too, decompose! God is dead! (The Gay Science, Book III, §125)
This is the frank but controversial message that the madman in The Gay Science brings to his fellow citizens of the modern world. God is dead because we have killed him. How? To understand this, one must sink into the very core of Christianity, like Nietzsche did. According to Christian belief, the earthly life is a horrible place filled with death, pain, inequality and natural instincts. All of this goes against the moral ethics of God, who promises his followers a safe place in Heaven. But in order to reach this Heaven, we must live our lives according to the laws and ethics of that world here on earth, and this is where the problem lies.
A rightful Christian lives his life according to the moral laws of Heaven, otherwise he's not allowed through the pearly gates and thus is condemned to Hell for all of eternity. This means that Christianity demonizes the earthly life and its natural laws, in favour of a world reduced of all unpleasant things inherent to this reality. What Nietzsche and many people like him in the modern age did was to slowly begin to openly criticize the very foundation of the Christian faith. Was there really a God? Did a Heaven really exist, and if so, was it something worth striving for?
But the very thing that led to the decline of Christianity in the West was the new scientific optimism of the Enlightment. During this time, man's capacity to human reason and objective truth was upheld, and religious faith came under attack for supporting a dead cause. Science and technological development would lead humanity into a better age of material wealth and prosperity. For Nietzsche, this age marked the point when God was "killed." We searched for the truth and came to find that there is no God. "Great," one might say, "we found that God isn't real and just some made up hocus-pocus fantasy for superstitious ignorants. Time for truth to reign!"
This is what many people during this time thought. They felt immediately relieved by knowing they no longer had to care for a God that didn't exist. But as Nietzsche noted, truth isn't always what we seek. When a truth we previously thought to be real is suddenly proven to be false, we instantly need something new to replace the missing truth with. He asked himself: if we don't believe in gods anymore, what are we to believe in? People were slowly beginning to ask themselves the same question, without coming to any conclusion. Suddenly a fate worse than ever had come true: man had abandoned his belief in the eternal gods, but without returning to something else. As Heaven had turned out to be a religious dream and the earthly life still represented what was ethically and morally demonized, man had nowhere to go. Alone, shattered by the despair of being caught in a world of horror, he was doomed to live in a void of emptiness.