I have come across few descriptions of “spirituality” with as much integrity and clear-seeing as this, by the renowned German philosopher Thomas Metzinger. He grasps the incommunicability of the meditative experience (read: non-rational, no-logical, mystic, etc.). As he writes in his essay, “Spirituality and Intellectual Honesty: An Essay” (2017):
“Spirituality is an epistemic stance of persons for whom the sought‐after form of knowledge is not theoretical. This means that the goal is not truth in the sense of possessing the correct theory, but a certain form of practice, a spiritual practice. To take the example of classical meditative practice, it is a systematic form of inner action, which on second sight turns out to be a certain form of attentive non‐action. The sought‐after form of knowledge is not propositional, it does not involve true sentences. Because it also does not involve intellectual insight, the sought‐after form of insight is not communicable by way of language, but at most can only be hinted at or demonstrated. On the other hand, it always remains clear that spirituality is not merely about therapy or about a sophisticated form of wellness, but that in a very strong sense, it concerns ethical integrity through self‐knowledge, a radically existential form of liberation through insight into oneself; and it is also clear that in many traditions, this involves some kind of mental training and practice, an inner form of virtue or self‐refine‐ ment. At the very beginning, then, there is an aspect of knowledge as well as a normative aspect, and this means that, in a very special sense, taking a spiritual stance on the world involves both insight and ethics. The spiritual stance is an ethics of inner action for the sake of self‐knowledge.” (emphasis mine)
Metzinger’s short-scheme definition of “spirituality” is exactly true, in my experience: it sees the ineluctable marriage of science and spirituality:
