Souter was appointed because they thought he'd do what he was told, like a Chicago alderman. As it happens, Justices serve for life and they don't have to do what they're told (this is not an accident). When you choose somebody for his weak will, you get what you pay for.
Then again, I'm tempted to note that Ruth Bader Ginsburg is praised for her "independent thinking" in departing from her party line, while poor Souter is "haphazard" for doing the same. Maybe Souter is a responsible adult with a conscience, who is well-informed about the law, and who makes up his own mind. I wouldn't put it past George Bush to have been so confused that he appointed an honest man by accident. Stranger things have happened, even in Washington. If there were exactly one acceptable interpretation of the Constitution, and if it were glaringly obvious to anybody just what that interpretation was, why would we have nine1 of these characters?
I'd rather think they're both space aliens sent here by inconceivably ancient forces of ultimate evil, but I'll take what I can get.
1 That "nine" there used to be "twelve", until
discofever graciously asked me what the hell I was thinking. The best excuse I could come up with was that "12" is nine in base seven, but that's pretty damn lame so I just fixed it.