One can administer rating scales to people who have taken a psychedelic drug and who have had a non-drug spiritual experience and compare scores. There have been studies comparing descriptions of ketamine and of DMT with descriptions of the near-death experience, which possesses “spiritual” characteristics. But no one with a real NDE, for example, has been given DMT or ketamine to ask him or her to comment on the degree of similarities. And, I haven’t seen any published data where a psychedelic is given to someone with a validated certified enlightenment, mystical, or prophetic experience. It is important to discriminate between the two broad categories of mystical-unitive and interactive-relational spiritual experiences in the construction and analysis of the rating scales. One could also compare functional brain imaging in those undergoing a particular type of non-drug state and those experiencing a psychedelic session. However, one would still need to assure a uniformity of type of spiritual experience psychologically.