There are a number of spiritual practices across traditions that are still based in a pre-scientific worldview. Consider fasting. Fasting was thought to clear our minds so we could hear from God. If we fasted long enough we would see things and hear things that we otherwise wouldn’t. Fasting is rooted in the Greek belief of some two thousand years ago that the body was bad and impeded hearing from the Spirit, which was good. If you wanted to hear from God, you fasted. Science now tells us that fasting lowers our blood sugar. Lower it enough and you will see and hear things you otherwise wouldn’t, but they aren’t from the Divine. They are from our glucose-deprived brains.
Consider the vision quest. The person heads out into the wilderness by themselves with minimal supplies and no shelter, often in an arid climate. Eventually their blood glucose drops and they become at least minimally dehydrated Then the God phone rings, but it is essentially the same process as fasting. We do damage to our bodies and minds and we hear and see things. We declare that they are from God, but they aren’t. Rather they are a consequence of the things our bodies do in an attempt survive our own foolishness. We don’t need to be delirious to hear from God. I would argue that when we are delirious we can’t hear from God precisely because we are impaired.
It’s long past time to move beyond the mistaken notion that it is ever good to do ourselves harm, especially in the name of the Divine. If something we once thought was from God is now understood to have identifiable physical causes then it was never from God. At times in our history we did any number of things we now recognize as foolish, often to put our supposed holiness on display. Perhaps we should consider that the urge to display our holiness in any manner is more a function of an unhealthy ego than preparation for a halo!