What does the title "His Dark Materials" mean?

"His Dark Materials" is taken from the epic poem Paradise Lost by John Milton. "His Dark Materials" is the title of the trilogy and that alone. "His", within the trilogy does not refer to a character, nor do the "materials" refer to Dust, the alethiometer, subtle knife, or amber spyglass. The phrase "His dark materials" only holds bearing within Paradise Lost. After the rebel angels are banished from heaven, Satan begins a quest from Hell to Earth. Before arriving at Earth he must make his way across an area where Chaos and night rule. Hot, cold, moist, and dry fight endlessly with chaos as the only director, and the battle can only end if God forces the four elements into their own worlds. In this context, the small excerpt at the beginning of the trilogy can be referenced, "His" refers to God who commands over the "dark materials" of hot, cold, moist, dry, and chaos.  more