Dr. Wouter Hanegraaff describes the effect of entheogenic substances on religion, esotericism, and neoshamanism over the past 50 years. He explains how the drug war prohibition necessitated that the practice of spiritual use of entheogens move into an underground esoteric tradition, and observes how modern commentators and academics often misunderstand or ignore that reality.

@28m, he describes R. Gordon Wasson's first trip to Mexico to study the Mazatec psilocybin mushroom ritual first hand, which later drew important figures like Timothy Leary and alerted the western world to the religious use of psychoactives. Wasson's publication of the mushroom ritual led to Terence McKenna's research into the fungus and other entheogens, catalyzing his career.

@42, he describes the idea which these early experimenters discovered, that "as human beings, we are able to obtain direct experiential knowledge of our own divine nature," a central idea of western esotericism as well as many religions around the world.

@49, he concludes urging us to take this phenomenon seriously, and to be aware of "our inherited blindspots regarding the role that entheogens have been playing in this context for at least half a century now. That role is not marginal but quite central."

I know the video is long but if you're at all interested in this topic it's a great lecture.