Chris Letheby writes for Psyche:
Mystical-type experiences are the phenomena that people most commonly feel to be spiritual. So, if we want to know whether spirituality is necessarily always focused on non-naturalistic ideas, one obvious approach is to ask people who’ve had such an experience what it meant to them. Qualitative researchers have done this, and the results are intriguing. Some subjects describe metaphysical visions of what the Zen writer Alan Watts called a ‘joyous cosmology’, but others do not. Instead, they emphasise changes in self-perception, feelings of connectedness, intense emotional experiences, and psychological insights. It seems that matters are not so simple as mysticism equating to non-naturalism.
Indeed, there is a lot of overlap between psychedelic subjects’ reports and existing philosophical accounts of naturalistic spirituality. Bringing together several such theories in his article ‘Spirituality for Naturalists’ (2012), the philosopher Jerome Stone extracts a core set of ideas:
“We are spiritual … when our sense of connection is enlarged … when we aspire to greater things … [and] when we ask the big questions. Note that these three – connection, aspiration and reflection on profound questions – are all forms of enlarging our selves, of breaking through the narrow walls of the ego.”