"Pulvis et umbra sumus" is the latin phrase for "we are but dust and shadow" used in Ashes to Angels. This statement is partially true, true enough for me to gladly expand upon it.
But we're more than that, of course. I'm sure the speaker of this line knows that. The statement in seemingly being so hopeless is actually a hopeful reassurance, as if to suggest that since we are but dust and shadow physically, we don't have to worry about that much. It humbles us. It associates us with the essence of the earth, reminds us that we're all in this together.
The part that is not dust and shadow is the soul. And I believe the soul never dies. Can never disintegrate. Can merely be moved from this plane to that, this experience to that. This dusty body to that dusty body.