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?