The Vatican is holding a big meeting of bishops, called a Synod, to discuss issues of the family. And one issue front and center is whether Catholics who are divorced and remarried can receive communion. Unlike my colleague Michael Brendan Dougherty, I can't imagine that Pope Francis will reverse Catholic teaching on the indissolubility of marriage.

According to Catholic doctrine, someone who is in a state of serious sin cannot, for their own spiritual protection, receive communion. And according to Catholic doctrine, drawn from the mouth of Jesus himself, marriage is indissoluble. If you were married in a valid Catholic wedding, then get divorced and remarried, you are committing adultery in the view of God, which is a serious sin.

Even in his own day, Jesus was accused of promulgating "hard teachings" about communion, and this is certainly one of them. Catholicism is the only major world religion that does not make allowances for divorce; in various ways, Protestant Christianity and Eastern Orthodox Christianity (despite the clear words of the Bible) make their allowances, as do Judaism and Islam.

And it is a hard teaching. It puts some people in impossible situations. Someone whose marriage fails early in life might have to contemplate the prospect of lifelong celibacy, and that can be tragic.

Still, this teaching isn't based on just a few phrases in the Bible. It's actually woven deeply into the entire logic of the Christian faith. To understand this, it's important to keep in mind two key aspects of Christianity: that the Christian God is a God of self-gift, which means self-gift is the meaning of life; and that Christianity calls everyone to moral heroism.

The self-giving God

In the Catholic liturgy, Jesus' teachings about marriage are interwoven with the account of creation in Genesis. The Bible is a symphonic document, with each part referring to the other parts, and the liturgy of the church — the organization that, historically, produced the Christian Bible as a complete document — highlights those resonances by putting different parts next to each other.

The overarching theme of the Bible is that God is a God of love, who creates a good world and human beings out of sheer generosity, so that these humans might enjoy absolute flourishing. When the world and human nature become damaged due to a cosmic catastrophe, God sets in motion a rescue operation to redeem his good creation. Throughout, the Bible describes the relationship between God and his people in terms of a marriage — a loving union that is a mutual self-gift of opposites. God's final victory over the forces of evil, when all of creation is finally made resplendent, is described as a marriage banquet.

According to Christian teaching, everything good that God has created — whether it's humor, or the beauty of nature, or relationships — is there to teach us in some way about his love, and to teach us to love in the way that he loves us.

And the way God loves us, according to the Christian faith, is in a specific mode: self-gift. Many faiths claim a God who created the universe; only Christianity teaches that this God so loves the world that he became one of us, and died and went to hell to save us. In other words, he gives himself completely, even unto total abandonment, and this gift, Catholic doctrine says, continues every day in the Eucharist, which is the real presence of God in every tabernacle and ultimately in every one of us.

To love the way God loves — which we are all called to do — means to give oneself completely, without holding back. Some are called to give themselves to others completely outside of marriage through celibate vocations, and some are called to give themselves to another person in marriage.

And, well, completely means completely. Jesus didn't step off the cross halfway through his ordeal and say, "You know what, at this point, I've given plenty with the scourging and stuff, that'll have to do."

Everyone knows marriage is hard. It is for richer and for poorer, in sickness and in health. Sometimes it sucks. But if we want to draw close to God, to answer his call of love, then we have to love — insofar as we are able, and insofar as he helps us — as much as he does. If God gives himself completely, then it means that the meaning of life is to give oneself completely.

The call to moral heroism

For most people in the West, the meaning of life is defined in a bland way: as feeling good about oneself, perhaps, and being nice to others. They believe that if there is a God, that's probably all he expects of us. That worldview is certainly incompatible with the Catholic doctrine of marriage.

Catholics believe that God thinks more highly of us than that. Catholic doctrine has no time for any bigotry of low expectations, soft or hard.

Catholic doctrine, frankly, sometimes asks the impossible.

What do you do when God asks the impossible?

If Catholicism's answer to this question was "just do it," it would be a monstrous and false religion. All of us are capable of the moral heroism we are called to, but all of us will stumble very hard along the way, and most of us will never reach our full potential. And if there's one thing everyone knows about Jesus, it's that he loves sinners.

But, see, here's the thing. Precisely because he loves sinners, Jesus doesn't offer them excuses; instead he offers them forgiveness.

There is a world of difference between those two. An excuse is a means to rationalize away what we did. Unlike excuses, forgiveness faces up to reality. Unlike excuses, forgiveness doesn't whitewash ugliness, it erases it completely. And unlike excuses, forgiveness allows us truly move on and grow.

Everyone knows, deep within their bones, that marriage is meant to be for a whole life. Anyone who has ever been in love knows that they were called to be with this person for this entire life. Anyone who has their eyes open also realizes that this is, indeed, a very hard calling. But pretending that the calling doesn't exist doesn't do anyone any good.

We're meant for more than that. We're meant for total love — and in a broken world, whichever route you take to that destination will involve trials and sufferings. But the call endures, the siren song continues. All of us know deep down that we are called by that love that never ends, that love that shakes heaven and Earth, that endures all things, that makes all things possible, a love that lights up the entire universe, the love that transforms the universe into an endless symphony of truth, goodness, and beauty. And nothing can ever change that.