We've probably all heard of the phrase to 'play Devil's Advocate,' referring to taking a side in argument that you don't necessarily agree with in order to stimulate the debate, but I'd bet that it's the case that only some of us actually know anything about the phrase's true meaning.
It's a fact that the Catholic Church occasionally decided that a person had been so noble, so laudable, so deserving of a place in heaven that they are officially recognised a 'saint' and given a free ticket- without the orthodox historical requirement of leaving a vast legacy to the Pope. However, until the charade was abolished in 1983, no-one was merely appointed a saint... oh no, each and every potential applicant for the position of sainthood was put through a tribunal, in a Vatican court, to establish whether they truly were deserving of haloed depiction.
It was in this tribunal setting where one could meet the Devil's Advocate. Literally the lawyer whose job it was to find holes in the person's character and attempt to disprove the credibility of the obligatory miracle which must be performed in order to receive sainthood. It would, however, usually be a pro bono task (perhaps due to the fact that Satan is unlikely to qualify for legal aid being in possession of many millions of valuable human souls.) This lawyer would face the less idiomatic God's Advocate, whose job it was to push for the exact opposite.
I therefore come to the crux of my point. Why would the expression 'Devil's Advocate' have come to mean playing a part in debate that you disagree with? Has the saying found its meaning based on an assumption that over the many centuries of canonization hearings, the people who have spoken on the side of reason must actually believe that the person in (what isn't strictly a dock, but probably should have been) was obviously deserving of sainthood... but it was right to have a two sided debate? The late Christopher Hitchens who took the job at Mother Teresa's hearing certainly wasn't playing the role just for debate's sake. He genuinely and stridently believed that she was a "bat from hell." However much I admire Hitchens, I would however be tempted to completely have ignored the Catholic Church's call for me to 'represent Satan' in such a hearing had I been asked. He did, and I have, better things to do than play their silly little game. There's no longer any place in the world for saints, and it's about time most were revealed as less than righteous, and more interested in their holy dogma than the good of mankind. Expressing that in Vatican court is a fantastic way to never get yourself heard.