Downey made the point to me that no intoxicant has a predictable response:
“Across cultures, intoxicants of all sorts have quite different effects: even alcohol has no uniform effect. In some places, it leads groups of people to fight, in others to cry to themselves, in others still, to raucous singing or dancing. Although the chemical may have a specific effect — such as emotional disinhibition or visions — the effect in the brain does not necessarily produce the same emotional or perceptual effect. Hallucinogens may make us prone to have visions, but they do not determine entirely what sort of visions they will be, or whether they will be a profound and life changing event, or a temporary intoxication.
To really have the sorts of effects that Sam Harris hopes for, you would need the symbolic resources and social support to leverage the hours of intoxication into serious insight. In a society hostile to visions, convinced that there is no higher form of consciousness than everyday awareness, I think it’s unlikely that most users would have the sorts of experiences that Harris describes. Some will, and they show us what’s possible; but they do not point the way to anything inevitable.”