Driddle said:
Faith, in the sense used for discussing matters theological, is what a person bases his belief on sans evidence. If you've got evidence of gawd's existence, then there's no need for faith.
That rather depends on who is discussing theological matters with. It is true that some philosophers have treated the idea of faith as belief sans evidence and that some theologians have attempted to come up with a way to accept that definition without being obviously apostate. However, at least for (theologically) conservative and historical Christian theology, you've got it exactly wrong and the faith/evidence distinction is a false dichotomy. C.S. Lewis characterized faith (I'm paraphrasing) as the steadfastness to continue believing and acting on what your mind tells you is true despite feelings to the contrary. The famous passage on faith in Hebrews also makes absolutely no sense if you read it with the "belief sans evidence" definition in mind. "By faith, Moses..." Moses had plenty of evidence so the author who ascribed Moses' actions to faith must have had something other than "belief sans evidence" in mind. From another theological quarter, you'd never get the idea that faith is belief without evidence by reading the late John Paul II's
Fide et Ratio.
Your definition may very well be the definition that is used when discussing theological matters with some people in some quarters, but it's not the accepted theological definition by any stretch of the imagination and accepting it actually inhibits understanding of a lot of both ancient and modern theology if it doesn't render understanding impossible. You'd get just as far understanding progressive thought based on Ann Coulter's definition of justice.
Complicating matters of faith vs. evidence is a funky mental quirk humans have that psychologists call "confirmation bias," which leads us to establish cause-and-effect relationships between all sorts of events even if such links are not justified. For example, I wear red socks and my team wins, I'm convinced that the socks and success are connected in some way. It works the other way, too, though: once a bias has been established ("I pray and good things happen"), the negative outcomes are ignored because they don't fit the bias ("Hnh. I prayed and nothing happened? Must not have prayed hard enough...")
What that means is that the layman philosopher will stubbornly maintain that he has seen "evidence" of gawd's existence via prayers and miracles, even though there's no way to track it back to the source.
This argument doesn't really hold water. There are more types of reasoning than deductive and inductive. Though it doesn't get the Sherlock Holmes literary treatement, abductive reasoning to unobservable phenomenon is an important part of certain branches of physics and the same kind of reasoning can be applied to the spiritual world. For instance, if one takes the biblical story at face value (or some other stories, for that matter; I refer to the biblical stories because they are the ones I'm most familiar with), the Moses heard a voice speak from within a bush that appeared to be on fire but was not consumed. The voice instructed him to take off his shoes--an instruction consistent with his cultural notion of holy ground and his received expectations of the divine. It then gave him directions that appeared to refer to events in his past and in the world around him. When he protested, it appeared to respond to his protests. It directed him to cast his stick on the ground and the stick became a snake. It directed him to pick the snake up and the snake became a stick again. It directed him to put his hand in his tunic and it appeared to become leprous. It directed him to do so again and his hand resumed its normal appearance. Then, as though it expected the demonstration of power to change Moses' mind, it repeated its directions.
Assuming that all of that happened as described, it would constitute evidence for the existence of a being that made the bush burn, spoke, appeared to understand what Moses said, and then caused the physical changes in his hand and staff. Dismissing it as confirmation bias would be ridiculous. (And that some people
would dismiss it as confirmation bias or hallucination is evidence enough that, all of the D&D magic, no matter how common would not guarantee belief either in the divine in general or any particular entity). The layman philosopher may be correctly or incorrectly reasoning that an unobserved (or even unobservable) entity is behind any of his particular experiences, but the principle of reasoning to unobserved causes for phenomena that need an explanation is sound. (And the materialist who always thinks that "natural" causes can (or will be able to) explain any given phenomenon can just as plausibly be charged with confirmation bias as one who believes that spirits are responsible for everything).
To bring the discussion back to D&D, I don't think that the core rules really offer any definitive explanation for why people might worship a deity. However, one rather ancient explanation that could be made to work would be because deities deserve worship in much the same way as a star athlete or a good man deserve admiration. (The phrase "hero worship" is not wholly metaphorical). Deities do things that people see as admirable and peoples' response is praise and admiration. (And, if you want to know why people worship evil gods... well, anyone who's lived through junior high knows that people praise and admire a lot of people who are rather repugnant). Obviously, that explanation would demand a far more active and direct connection with the gods than is customary in D&D (where spirituality often resembles Christianity with all the Christian elements removed (no wonder it's often vacuous)). However, it might well resemble the world portrayed in the Illiad or Exodus where the gods or God showed up and interacted directly with mortals rather frequently.
