What kind of faith is Arnold talking about in "Dover Beach"?

By having two people in a small room overlook a great
expanse of nature, especially the white cliffs of Dover, the faith that remains is
personal fidelity, based on love between people. Nothing else is sure; the beauty, joy,
and other human experiences which we wish were certitudes—all these are illusory. The
private world of the little room assumes the full weight of human life and freedom.
Therefore, what remains is the commitment that individuals make to fidelity, and this
commitment enables people to conquer all that is vulnerable and transient. It is a
unique contrast; the love of people versus the rest of the world. The only thing that is
true is what you have between you and the person you love.