Mystical experiences involve an intensely felt fading of the sense of self and/or feelings of increased connectedness, up to a sense of complete unity. In ordinary consciousness, there is a distinction between self and everything else, but during such experiences the sense of self can fade and become part of everything else. Neuroimaging of meditators and nuns shows that brain regions that differentiate self from the world are inhibited during these experiences.
Spiritual experiences can be triggered by a variety of scientifically identified factors, including specific circumstances, personal dispositions, mindsets, rituals, practices, and psychoactive substances like psychedelics. Future neurotechnologies may also play a role. This chapter, drawing on the Jamesian approach of setting aside theological questions, summarizes research on the conditions that make such experiences more likely to occur.