Our discussion about religious experience got me thinking about what actually counts as evidence or authority. It seems to me that there are so many levels of possible deception that make it impossible to determine whether a religious experience is really genuine. There is the possibility that the person is lying, and did not really have the experience. Then there is the possibility that they really did have the experience, but it was a dream or hallucination or from some other natural explanation. Last there is the possibility that they really had the experience, and it really was God or something supernatural communicating with them, but that thing itself is actually deceiving the person. Most people of faith would be uncomfortable with the possibility that their revelation is genuine, but God is actually lying to them, but I bring it up simply as a logical possibility. It is also possible that Satan or whatever other supernatural being is posing as God to give someone a revelation. Deception can enter the picture at any point in this chain, and even if you are the person experiencing the revelation, how can you even determine its validity, let alone convince anyone else of it?
This is important because ultimately all religion comes down to a spiritual experience of some kind. Christians take the Bible as their authority, but what gives it its authority? The revelations given to the prophets and other authors, and later Paul's vision of Jesus are all varieties of revelation, as is the recitation of the Qur'an to Muhammed. Even the canonization process ultimately goes back to asking what authority the compilers of the Bible had to do so, which is connected to apostolic succession and their own religious experiences. What makes one legitimate and not the other, and how do you know? We can't say that all religious experiences are equally legitimate because obviously some are mutually exclusive. So we must have a way to distinguish what is real from what isn't. There seems to be no way to do this besides one's own personal conviction in the strength of their experience, but anyone from any other faith has the same argument and equal convictions of their own.