scienceguy it comes down to the underlying theology of the faith healing movement (which I stay well away from, fyi). They do believe God works through regular doctors etc. but they believe that if everyone had enough faith then all sickness would end and doctors would all need redundancy payouts. So for the most part they roll with regular medicine, but for certain things believe that the more faith they have the more likely something is to be healed. Hence the dramatic yelling and hallelujahs and cheesy music, all of which helps people get into an emotional state where they can have stronger belief.
Of course in practice it doesn't work quite as well as it says on the tin. It's mostly based on observations of the placebo effect, which reduces or removes pain and can even facilitate (some) healing based on the extent to which the subject believes in the placebo. Since most folks aren't overly familiar with the effect they'll tend to interpret a reduction in pain they believed was coming as a miracle. This is why in a sense it does work, just isn't all that miraculous and isn't about to regrow any arms.
Bear in mind however that the faith healing movement (often referred to as word-faith or third-wave in the biz) is very different to the question of whether God can or does heal in response to prayer etc. - most Christians believe that God can/does sometimes, but that this isn't at all conditional on the faith level of the person, nor is it on tap and effectively guaranteed (with enough faith) as the WF people would say it is.
Last edited by vijil : 11-10-2012 at 12:15 AM.