The speaker sees that the world looks beautiful, as he describes it in the opening stanza. However, he states in the closing stanza that the beauty is illusory and deceptive. The world
To lie before us, so various, so beautiful, so new,
Hath really neither joy, nor love, nor light,
Nor certitude, nor peace, nor help for pain...
We have lost all these things with our loss of religious faith. All we have left is temporary, transitory human love. The speaker does not seem to see this as a solution but only as a residual mutual consolation for everything that has been lost. Instead of being alone in the universe, they are alone in it, clinging together. The two lovers call to mind Adam and Eve in Genesis.
Unto the woman he [God] said, I will greatly multiply thy sorrow and thy conception; in sorrow thou shalt bring forth children; and thy desire shall be to thy husband, and he shall rule over thee.
And unto Adam he said, Because thou hast hearkened unto the voice of thy wife, and hast eaten of the tree, of which I commanded thee, saying, Thou shalt not eat of it: cursed is the ground for thy sake; in sorrow shalt thou eat of it all the days of thy life.
We have eaten of the tree of knowledge, and now we know that we are mortal and naked. Both the speaker and his paramour will grow old and die, and the speaker is not even sure that he will continue to love her or that she will continue to love him. He sounds frightened. His fear has been called "existential angst." He sees himself and his loved one as pitifully small, fragile, and helpless in a vast, meaningless, godless universe. She says nothing.
This vast, empty universe is growing larger all the time. Scientists are now telling us that the universe is infinite, that time is infinite, that the Big Bang was only one of a limitless number of big bangs (or bigger bangs?) creating more universes. In the meantime our little planet gets smaller and smaller--and we get smaller and smaller, and more insignificant, along with it.
It seems hard to understand why the speaker should want to depress his paramour with such morbid thoughts at such a time. They seem to be on a honeymoon in an idyllic setting and will probably be making passionate love before this night is over. He tells her there is "neither joy, nor love." What is she supposed to make of that? There is no love in the world, and yet he wants her to love him? Does he love her? And if so, why is he spoiling their evening? A feminist critic might say that he is trying to frighten her so badly that she will feel she has nothing in the world to cling to or believe in--except him!
If this is a new romance, she should be able to see that she is getting involved with a man who likes to dwell on depressing thoughts and doesn't mind sharing them with her. This would be a very good time for both of them to forget about the
confused alarms of struggle and flight,
Where ignorant armies clash by night.
If he really loved her he could forget about the retreating Sea of Faith for at least this one night. But since he can't dispel these morbid images from his mind, he shows that he does not place too much faith in the consolation of human physical and spiritual intimacy. The poem is disturbing without being profound. It has been satirized on more than one occasion.