I just read Sam Harris’ post from a few weeks ago entitled Drugs and the Meaning of Life. Harris makes several good points regarding drugs and altered consciousness – it’s a good read. I’d just like to highlight how this topic ties in with scientific understanding of “religious experiences.”
Religious people will often claim to have subjective experience that corroborates their metaphysical claims. “I can feel God in my heart”, and all that. We know that altering the chemistry of the brain can cause people to have mystical or numinous experiences, feelings of having transcended normal consciousness or reality, and so on. Brain surgery can cause this, as well. Therefore, one cannot use these religious experiences as evidence that their religion actually is true, when they very well could be illusions caused by certain states of the brain.