Mother Night question

It is mentioned in Goethe's Faust, in a speech by Mephistopheles:

I am a part of the part that at first was all, part of the darkness that gave birth to light, that supercilious light which now disputes with Mother Night her ancient rank and space, and yet can not succeed; no matter how it struggles, it sticks to
matter and can't get free. Light flows from substance, makes it beautiful; solids can check its path, so I hope it won't be long till light and the world's stuff are destroyed together.

That text is quoted in the Editor's Notes at the start of the book, claiming that the title was created by Campbell himself.

I still don't understand it though. Mother Night is the darknesss that existed before the creation of the universe? I'm not sure what that's got to do with the story.

I'm not sure that i understand it either but my guess is that the ambiguous relationship between Darkness and Light which Mephistopheles alludes to (once whole, one born of another, now enemies) is of the same nature as the ambivalent relationship the
characters have with one another (especially Campbell, "Resi" and the painter) and, more importantly, with themselves. There's a constant struggle between light and darkness in every man's soul (that's what Soljenitin said, right?). In some darkness wins (the painter), in some the light wins ("Resi") and in some the battle's result is inconclusive (Campbell).

I'm not sure either but I love this book. As for you guys was it a hit or miss with you guys? And why did or didn't you like it? I liked it because it's about World War II and lately I've been in a phase of wanting to read historical fiction novels about World War II. I loved the characters. I think Kurt Vonnegut Jr. did a good job introducing them. As well as keeping them consistent in the story line. The description of things and places was very good as well in my opinion.