“To most people who are even moderately experienced with entheogens, concepts such as awe, sacredness, eternity, grace, agape, transcendence, transfiguration, dark night of the soul, born-again, heaven and hell are more than theological ideas; they are experiences.” - Thomas Roberts
This phrase is quoted in "Sacred Knowledge" by Richards, yet I find it the most suitable summary of this overview of scientific research on psychedelics and religion.
We hear about mystical visions from LSD ("acid"), psilocybin ("shrooms"), and DMT from many "spiritual but not religious" people and self-proclaimed shamans. But how does it relate to vision by ordinary people (ones who never tired, and wouldn't try if it weren't for legal, scientific research)?
And how does it relate to prayer, mediation, and mystical visions by Christians, Jews, Buddhists, and Hindus? How do monks and priests compare their psychedelic experience with their regular practice? Do they all turn to Zen Buddhism, or entrench in their religious background?
Regardless if you are deeply religious, or a non-spiritual atheist, I believe you will reconsider a few things after reading this book.