there's another force as well, one every bit as real as the God ..., 

and that it works consciously to bring all our decent impulses to ruin. ..., 

but a kind of demon of discord, a prankish and stupid thing

 that laughs with glee when an old man sets himself on fire trying to light his pipe

 or when a much-loved baby puts its first Christmas toy in its mouth and chokes to death on it.