In Buddhism, enlightenment (bodhi, "awakening") is what Siddhartha Gautama is said to have reached under a fig tree at Bodh Gaya, in India, around the 5th century BC, ending the cycle of rebirth. Zen, Hindu and Western mystical traditions all have their own versions: a direct and lasting insight into the nature of mind and reality, usually after years of discipline.
English uses the same word for the Age of Enlightenment, the 18th-century movement of Locke, Voltaire and Kant that put reason, science and free inquiry above authority. Kant defined it in 1784 as humanity's emergence from its self-imposed immaturity, with the motto Sapere aude, dare to know. The Bavarian Illuminati, "the enlightened ones", founded in 1776, took their name from the same idea.
The two meanings meet in the lab. On Good Friday 1962 a Harvard graduate student gave psilocybin to divinity students, and most of those who got the drug reported a mystical experience. Johns Hopkins revisited the question under strict controls in 2006. Whether a pill can deliver what monks spend lifetimes on is still argued; the usual esoteric answer is that it can open the door, not walk you through it.
