Descartes doubted his way down to a fundamental. Most of the world’s traditions never doubted their way anywhere — they inherited theirs, and that’s not a lesser method, just a different one.
First-principles reasoning has a specific shape: strip a problem down through individual doubt until you hit something self-evident, then rebuild from there. It’s a method built on an implicit claim — that a single reasoning mind, working alone, can arrive at bedrock truth by subtraction. Philosopher Alasdair MacIntyre’s critique of this Enlightenment inheritance is that it treats rationality as if it existed outside any tradition, when in fact every standard of “self-evident” is itself inherited from a particular history, community, and practice. There is no neutral standing-ground from which to reason “from scratch” — the ground is always already someone’s tradition.
That’s the gap a “fundamental” in the non-normative sense points to: an epistemic starting point that a tradition treats as beyond question, not because an individual reasoned their way there, but because it was received, practiced, and lived into over generations. Examples that don’t reduce to first-principles logic: jihad — commonly flattened in translation to “holy war,” but literally meaning striving or struggle, and understood within the tradition as encompassing an inward struggle against the self before any outward one — and tazkiya al-nafs, the purification of the self, treated as a fundamental discipline rather than a conclusion anyone argues their way toward. Neither is “irrational.” Both are simply fundamentals of a different kind than the ones first-principles thinking is built to find.
Source: MacIntyre, A. Whose Justice? Which Rationality?, 1988; Porter, J. “Tradition in the Recent Work of Alasdair MacIntyre,” 2003; Saritoprak, S.N., Exline, J.J., & Stauner, N. “Spiritual Jihad among U.S. Muslims: Preliminary Measurement and Associations with Well-Being and Growth,” Religions, 2018.