Thread title: Non Muslims, how do you explain the existence of the Quran/Sincerity of the Prophet?
Sorry for the delay in getting back to you, have been a tad unwell.
I believe that the 'religious experience' is fundamentally the same for all of us. As there is, and can only be, one Reality, to be sought and accepted, there can only one Reality that can be found. What differs is our perception of that Reality, and how we present it to ourselves and others.
We all have religious experiences, in widely varying frequencies and intensity depending on the individual. Every religion has them, those same flashes of insight into Reality, be it the satori of the Zen Buddhist, being 'spoken to' by God in response to a Christian's prayers, and so on.., but I believe all represent the same thing. What differs is what we believe these experiences represent, and those beliefs are inevitably (with one exception) set within the framework of our existing beliefs, and conditioned by our experiences.
Every so often along comes somebody, a 'Great Sage' if you will, whose insight and depth of understanding far exceeds that of the rest of us, be it the Buddha, Prophet Mohammed, Jesus, Lao Tsu, or those unknown authors of the Upanishads. All these people, though, were presented with two fundamental problems. The first was how to present what they had learned to others. This differed according to individual and cultural circumstances at the time. The Buddha, for example, had an 'audience' essentially of religious mendicants, seekers of Truth like himself, and that is relected in the teachings of the Tipitaka. In a sense, therefore, he had a rather easier time of it than Jesus or Mohammed who listeners were generally 'ordinary' people rather than religious seekers.
The Buddha, though, was the only one to fully realize that the entirety of our experience is conditioned and therefore illusory, and point in the direction of true Reality. The Buddha also realized that different teachings were necessary according to the levels of spiritual achievement (and accumulated karma) and adopted what he called 'skillful means' in catering his teachings to his audience.
Jesus and Mohammed remained contrained by their own conditioning, and that same need to cater to their audience, and hence interpreted and represented reality in the form of a God..both realized, of course, that there only being one Reality there could only be one God, at least in the sense of an omnipotent one. Unfortunately, as a consequence of their limited understanding much excess baggage got bolted on to the immense spiritual wisdom of the teachings of Jesus and the Qur'an, such as the very anthropomorphic presentation of God by the former tradition is obvious), and the inclusion of various regurgitated myths and social and legal elements in the latter.
Both Christianity and Islam generated 'mystic' movements or orders that recognised and tried to remedy it; it is perhaps the biggest tragedy of the monotheistic religions they were generally slapped down by a conservative and desperately unimaginitive and unenlightened mainstream.
Just to make clear that all of the above is my opinion, I can't 'prove' any of it. I realized long ago that you can't 'prove'
anything important when it comes to religion, and it's generally futile to try. I could quite happily, though, explain why I am a Buddhist rather than a follower of another religion (indeed I already have elsewhere), but that probably would only derail your thread again!