Stanza 4 Summary

Get out the microscope, because we’re going through this poem line-by-line.

Ah, love, let us be true
To one another! for the world, which seems

At the opening of the last stanza, we're back where we were at the beginning of the poem, in the room at the edge of the Channel.
The speaker finally lets us know who's he's talking to: his "love."
We spent the whole last stanza hearing about the fate of the world, and the metaphorical ocean of faith. So this feels like a pretty big shift. Suddenly the speaker's tone is personal, intimate, even desperate, as if he was clinging to his love to escape the terrifying things he's just been describing.
The idea of lovers being "true" to each other also picks up on the image of lost faith from up above. Even if the world has lost its faith, maybe they, in their small way, can hold on to some of it.
But note the enjambment between lines 29 and 30. First, he says to his love, "let us be true." That could be a more general statement about personal integrity. But then, squish it up with line 30, and you realize that he wants them to be true to one another, which is a much smaller, more intimate idea.
Maybe, just maybe, the idea of being true in the modern world is just too big to handle. So in the end, all we can do is be true to one another. Let's see if that plays out in the final lines of the poem.

To lie before us like a land of dreams,
So various, so beautiful, so new,

There's been a contrast running through this whole poem. On the one hand, there's the pretty view of the moonlit water that opens the poem. So in the present, in the world the speaker and his lover can see before them, things seem pretty much okay.
This happy world is "various" (that just means full of variety) and of course beautiful and new. We think there might be a little allusion to the story of Adam and Eve, the couple alone together with a beautiful new world before them. Do you agree?
There's also a hint of trouble in the way the speaker calls this "a land of dreams." On the one hand, that might mean that it's wonderful, but it might also suggest that this beautiful world is somehow unreal, which makes it all the more precarious.

Hath really neither joy, nor love, nor light,
Nor certitude, nor peace, nor help for pain;

Now we see the truth, (or at least as the speaker sees it). It's not that the world is part good and part bad. It's that the pretty part, which you can see, the world of calm night and moonlight and peaceful beauty is an illusion. It's the world he hears in the roaring of the surf that is real. And it's awful.
The reality of the world is nothing but grim chaos. All of the things that should make the world wonderful are gone. There is no joy, love, light, certitude (that means "certainty" or security) or "help for pain."
The speaker has clearly lost that faith he was talking about in the third stanza (lines 21-28). One thing faith can do for you is allow you to believe in order and goodness in the world even when all you see is ugliness and pain. Our speaker has lost that ability to believe in order, and sees only the nightmare.
Maybe this is just Shmoop, but we think that even though these lines are grim and sad, they are also kind of beautiful. There's something so sharp, so simple, so raw in the way the speaker cuts away all those wonderful things, one by one. We're gearing up for one heck of an ending, Shmoopers.

And we are here as on a darkling plain

Arnold brings the whole thing to a crashing finish here, with a famous simile. Yep, this is one for the ages.
He begins the simile in this line, comparing the faithless ugliness of the world to being in a flat and lightless place ("a darkling plain"). That's just one gloomier image in what is shaping up to be a pretty dark ending to this poem.

Swept with confused alarms of struggle and flight,
Where ignorant armies clash by night.

The poem slams shut on us with the end of this final simile that the speaker began in line 35.
The speaker and his love are not just stuck in the dark, but they are "swept" by noise and confusion. People are struggling, running away (in "flight") and sounding alarms.
The world is not merely a dark and comfortless place. It's a battlefield. But on this battlefield, the fighters can't see each other.
They are fighting at night, and presumably killing their friends as well as their enemies. There's no marching, no even lines, no fancy hats and polished buttons. Just misery, pain, terror, and confusion—a clash.
We've come a long way from the scene of peaceful beauty that opened this poem. The mask has been ripped off the world, and "Dover Beach" has shown us the chaos and ugliness within.