What is "negative" and "positive whiteness" in "The Dagger with Wings"?

Question

In "The Dagger with Wings" by G. K. Chesterton, the author was describing the falling of snow,that appeared through a barely opened door, saying:

What he had seen shining through the crack was not only the most negative whiteness of daylight but the positive whiteness of snow. All round, the sweeping fall of the country was covered with that shining pallor that seems at once hoary and innocent.

What's meant here by negative whiteness and positive whiteness? Does it simply mean dismal and delightful?

Answer 1

Normally, if a door is open a crack, at the bottom of it you will see something dark. It might be the grass, or dirt, or whatever else is outside the door. Above that you will see whiteness. That whiteness isn't a thing - it's the absence of things, emptiness, daylight. That's "negative" space -- the lack of stuff to see.

But in this case, surprisingly, the white is snow, perhaps up against the door, perhaps filling the air because it's falling very thickly, certainly covering the grass and dirt and whatnot that you might see out of the door. This is "positive" space, space filled up with stuff (snow in this case), and there's a hint in this wording to make you feel that the snow itself is emitting light and is a source of whiteness, though that's not literally true.

While the words aren't being used to mean good and bad, the fact that they also carry those meanings probably sets you up to like the snow from this description. The primary meaning is around absence or presence of stuff.