In the last stanza of "Dover Beach," Arnold talks about the falseness of the world: how everything appears to be beautiful and new but is truly empty of love and joy and light.
However, the speaker asks his lover that, even in that world of deceit, they should be true to one another
I realize it's been 2 weeks since you have asked this question, but I am going to answer it for other people who don't know the answer. Hope you don't mind, but if you do have a complaint you can message me.