Christianity has been criticized loudly in modern times for being a so-called "pie-in-the-sky" religion. Karl Marx popularized the idea that religion is the opiate of the masses; his thesis was that religion was invented and used by the ruling classes to exploit and oppress the poor people of the world and to keep them from revolting. The promise of "pie in the sky" was designed to encourage them to be good workers and to obey their masters—their reward would be deferred to eternity.
But one cannot take Christianity seriously without seeing the central importance of the concept of heaven. There really is a "pie-in-the-sky" idea that is integral to the Bible, and especially to the New Testament, and I'm afraid we've lost our appetite for the delights God has stored up for his people in the future.
From time to time, pollsters have asked Christians to name their favorite chapter in the New Testament. When polls like that appear, there always seem to be two chapters that come in first and second. The chapters that vie for the greatest popularity in the New Testament are 1 Corinthians 13, the great "love chapter," and John 14.
As John 14 begins, Jesus is speaking to his disciples in his last great discourse with them in the upper room on the night in which he was betrayed, the night before his execution. Verses 1 and 2 say, "Do not let your hearts be troubled. You believe in God; believe also in me. My Father's house has many rooms; if that were not so, would I have told you that I am going there to prepare a place for you?" Jesus begins this part of the discourse with an admonition, an imperative to his disciples. He tells them, "Do not allow your hearts to be distressed or disturbed." This is a call to trust and to faith. He then goes on to reason with them in a succinct but profound manner. Because these words are so comforting to us, we may too easily gloss over part that comes next.
Jesus says, "Do not let your hearts be troubled," and then he makes an assertion about the disciples. He says, "You believe in God." He doesn't ask them if they believe—he knows that they do. That's his first premise. He goes on to say, "Believe also in me." This is central to the testimony of the New Testament—it is God who certifies and verifies the identity of Jesus. By endowing Christ with miraculous power and raising him from the dead, God certifies that this is his beloved Son. Three times in the New Testament it is recorded that God speaks audibly from heaven, and on all three occasions the announcement is substantially the same: "This is my beloved Son."
In one case, the voice continues, "in whom I am well pleased." Another time it says, "Hear him." Jesus is telling his disciples that God the Father both sent him into the world and bears witness to his identity in the world; now, the night before he is to die, Jesus tells his disciples, "You believe in God; therefore, believe in me."
Why does Jesus start with the premise that they believe in God? There's a real sense in which that proposition is the controlling idea for one's whole understanding of life, of the world, of death, and of heaven. If there is no God, there is no reason to have any significant hope for the continuity of personal existence that we call life; and yet, if God exists, what would be more ridiculous than to assume that he creates creatures in his own image who are destined to live as grass for a season, only to perish with all of their memories, all of their hopes, and all of their labor ending in meaninglessness?