As a text, Mother Night is pretty self-aware. It even offers us an explanation of its own title, if we look outside the borders of the story a bit.
Remember how Vonnegut plays at being the meticulous editor of a "found" memoir instead of admitting he's the author of this novel? Great. Well, in his carefully crafted Editor's Note, he offers an explanation for the title of the whole work:
The title of the book is Campbell's; it is taken from a speech by Mephistopheles in Goethe's Faust. As translated by Carlyle F. Maclntyre (New Directions, 1941), the speech is this:
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. (Ed note.11)
Whoa, hold up. This title is from Faust? Okay, okay. We can parse this out. First off, we've got Doctor Faustus. That's a play written by Christopher Marlowe during the English Renaissance that was based on a pan-European legend. In this play, Doc F sells his soul the devil for knowledge of everything. Like, everything. It's tantamount to God's knowledge, which Adam and Eve got kicked out of the Garden of Eden for trying to taste.
So where does this Goethe person come in? Oh, we're so glad you asked. Johann Wolfgang von Goethe was a German poet and playwright who wrote his own, even more famous version of the Faust legend. Are there any big differences between Marlowe's and Goethe's text? There are. Here's a big one: while in Marlowe's play, Faust gets sent straight to tarnation for his intellectual crimes, in Goethe's play, Faust gets to go to heaven because—get this—God rewards ambition.
Okay, it's a little more complicated than that, but dude, we know. A text like this has major implications in the 20th century, when the world is at war over Hitler's quest for world domination. The Nazis didn't care about the actual meaning of any text; they just used what they liked.
In any case, let's get back to that quote. Mephistopheles—that's the devil—gives us a little metaphysical backstory about himself, telling us he was part of the first "stuff" (darkness) that light sprang from (when God said "Let there be…"). He's more than ready for the time when Mother Night and capital-letter Light destroy themselves together. Fun. Translation: he's ready for the apocalypse.
Putting it all together, what do we get? We see that massive, overreaching ambition—and the attempt to prop it up with propaganda—is what can actually bring about the end of the world.
Yep.