Theory of Revelation
As I see it revelation is necessary for faith. Some one, some tradition, or some relic must impart the articles of faith in order for us to know what to believe that we can't discover for ourselves. I feel revelation occurs when a person gains access to the Truth. This Truth is much greater than knowledge, or even wisdom. Think of pulling back the curtain in the Wizard of Oz or steping out of Plato's cave and staring at the sun. In my tradition the source of the Truth is God, so I will speak of God, the source of Truth without excluding other names for the source of Truth.
In one thought experiment I imagine that when God provides revelation to a person it changes them in a dramatic way. I imagine that if God were to provide the complete Truth to someone they would then be God. We don't find this in our history often and I feel that either full knowledge of the Truth is exceedingly rare or it tends to be fleeting.
In a second thought experiment I imagine God providing partial access to the Truth. This kind of revelation might be common and include anything from insight to prophecy. Again I expect a dramatic change, but not that the person becomes like God. Since the person is not like God they only have access to part of the truth and they have less than God-like ability to communicate the Truth.
My theory assumes that revelation is uncommon, incomplete, and impossible to communicate fully. This understanding of revelation allows for plural belief, and for rigorous vetting of the nontruth presented with the Truth.

Keep in mind I don't think that I have any answers about faith. These ideas are being worked out in my mind and might only be helpful for me.