You know the song. Sung sweetly and simply, it asks the listener to imagine a world of harmony and peace. So goes the refrain: “You may say I’m a dreamer/ But I’m not the only one/ I hope someday you’ll join us/ And the world will be as one.”

So popular is Lennon’s hymn that it is not rare to hear even Christian groups playing it. They are no doubt attracted by what appear to be a Christian longing: “A brotherhood of man/ Imagine all the people/ Sharing all the world...”

Yet the core of “Imagine” is a nihilism that is completely incompatible with revealed religion, let alone Christianity. Lennon imagines a world in which everyone gets along because there are no differences between them. There are no differences because there is nothing to believe in.

“Imagine there’s no heaven... No hell below us... Imagine there’s no countries... Nothing to kill or die for... And no religion too... Imagine no possessions... No need for greed or hunger...”

The mundane observation is to note that a world without private property was given a good try and the results were known long before Lennon wrote his song. Communism abolished many rights, but it did not abolish greed or hunger or poverty.

The deeper observation is that to live in a horizon determined only by this material world — no heaven, no hell, no religion, no great causes to give one’s life to — is not to be liberated, but rather locked into the narrow circumstances of this world, with all its manifest suffering and pain. Lennon goes so far as to lock us in the present moment alone: “Imagine all the people/ Living for today...”

The measure of character and responsibility, regardless of religious faith, is precisely to prepare for the future, to live for something, to create and build something that will endure, to provide a better piece of the world for one’s children. To live only for today is the measure of childishness and immaturity. In the wealthy parts of the world in which “Imagine” is so popular it is not surprising that the childishness it advocates has led to actual childlessness. A people locked in the present choose not to have children, the fundamental sign of hope in the future.

“If that which is envisioned here were to be realized, the world would be poorer and more squalid than we can imagine,” Fr. Raniero Cantalamessa, the preacher of the papal household, once preached in a sermon for the Holy Father, commenting on the popularity of Lennon’s song. “It would be a drab world in which all differences were abolished, where people are destined, not to peace, but to tear each other apart because ... where everyone wants the same thing, (desire) will be unleashed and with it rivalry and war.”

A world without God in the hope that somehow man would be better left entirely to his own devices, that’s at the heart of the new atheism. It is fundamentally an imaginary world, not only because the religious impulse is deep within the heart of man, but also because the historical evidence demonstrates that mass slaughter is the first order of business for societies that formally banish God.

The aspiration for universal brotherhood of which Lennon sings finds a different answer in the Christian Gospel, where Jesus prays that “they might be one” precisely as He and the Father are one. The unity we desire here is only possible as a gift from the unity of God — the three who are one. And the purpose of this unity, Jesus further prays, is that the world might believe. Unity is beyond us on material grounds alone, so we need to receive it as a gift from God. In acknowledging that gift, we profess our faith in the only source of true unity and lasting peace.

John Lennon is the minstrel of the new atheism, and it holds that religious faith is something imaginary itself, and therefore just another set of imaginings alongside whatever else the human heart can conjure up. In Advent the Church waits anew not for something imaginary, but Someone real. Only what is real can fulfill what we imagine.