With all of this debt ceiling shenanigans going on, and all the hemming and hawing about the deficit, it's worth it to take a look at how all of this stuff actually functions.  What does it mean, really?  Why do we care?  How many angels can dance upon the head of a pin, and so on?  I've been thinking about it a lot recently (taking time away from more important things, like the NHL offseason).  Today though, I read this post by Yglesias which put a lot of what I was trying to say into shape...