Don't worry. Despite what it sounds like, "The Canonization" is not a violent poem. We promise that no canons are fired during the course of this poem. In fact, Donne has a very different idea of "canon" in mind altogether.
In this case, canonization refers to the process by which a holy figure becomes elevated by religious officials to the formal position of saint. It sounds like a great gig, we admit, but you do have to be dead (among other things) to qualify.
You know what, though? The speaker of "The Canonization" is not going to let a little thing like death get in his way, not when he has the power of fantasy in his hands. The fourth and fifth stanzas construct an elaborate, metaphorical scenario by which the speaker and his lover a) die, b) become immortalized in poetry, c) are made saints by those who read these poems, and then d) receive prayers from the poor schlubs left back on Earth who aren't capable of loving anywhere near as well as they are.
It's a pretty far-fetched idea, we have to admit. Donne is actually describing lovers who become saints not for doing good deeds or being especially pious, but for being good at loving each other. On one hand, this seems like a pretty smug and self-serving fantasy. Who likes to hear a couple brag about how great they are at being a couple? On the other hand, though, this is a pretty profound dig at organized religion.
Think about it: most religions tend to talk about love as it relates to either a love of God or a conventional love between man and wife in a nuclear, baby-producing family. That's not what the speaker's describing in this poem, though. This is the kind of wild, romantic love where you seem to melt into the other person and lose yourself totally in the experience. It's not exactly the stuff of Sunday sermons.
And yet, maybe it should be. At least, that's one way to read both this poem's title and its central conceit. Why can't romantic love be equally as redeeming for humanity as religious piety? Why shouldn't we be canonizing remarkable lovers, just as we canonize those who express their love for the fellow human beings in non-romantic ways?
These provocative questions are at the heart of "The Canonization." Regardless of how you might answer them, there's no denying that Donne's poem is a celebration of romance, and a shot across the bow of religious convention.