Cosmic Trigger: self induced brain change, from wikipedia

Cosmic Trigger I deals with Wilson's experiences during a time in which he put himself through a process of "self-induced brain change" as well as vignettes of his earlier life. The main discovery of this process—which, he tells us, is known in certain traditions as Chapel perilous—is that "reality" (although a noun in most Indo-European language systems, and therefore[citation needed] commonly conceptualized as being a definite, unchanging "'thing") is mutable and subjective to the observer.