Some have theories and others faith, but all are One from the source that designed reality in such a way that makes discovery of its origin impossible. It is true that some have personal proof of God, but they didn't get it through efforts of the body, which is a part of the One. After becoming enlightened about the origins of physical matter, or the universe, that indeed it is all an elaborate illusion with no tangible essence beyond imagination, but not your imagination, your foundational understanding shifts away from everything known, and allows for input of truth. Before this phenomenon, or enlightenment, it is impossible to comprehend beyond current reality. Those who make it this far, which included the Buddha, and stop spiritual progression, rest upon non-duality, or monism as their belief system, which still falls short of the discovery of God, as it was all intended in the first place. Following the admonition of Jesus, "to love God beyond all boundaries" one may, or can, discover God, but only upon the principle of paradox, which if discovery were not to occur, God would cease to be God. The problem of course for these rare individuals is, they possess something impossible to convey to You! And so all the others simply fall back upon their base instincts of denial and criticism, which leads further down the rabbit hole within this illusion.