The phrase philosophia perennis was coined by Agostino Steuco (De perenni philosophia, 1540), a Vatican librarian arguing a single wisdom ran from ancient theology to Christianity. Leibniz borrowed the term (1714 letter to Remond). Aldous Huxley's anthology The Perennial Philosophy (1944), assembled after his Doors of Perception experiments, defined the modern canon: divine ground, divine spark, liberation through knowledge of both. Academic critics, notably Steven T. Katz (Mysticism and Philosophical Analysis, 1978), counter that mystical experiences are shaped by tradition, not evidence of one.
Perennialism powers the 'all paths up one mountain' framing of modern spirituality, a comfort that quietly demotes every tradition's hard claims to local dialect. The traditions themselves, most of which deny they are dialects, did not consent to the merger.
The perennial claim is unfalsifiable in a specific way: anyone who finds unity confirms it, anyone who finds difference is declared not deep enough. Katz's constructivist objection stands: the experiences are real, but the 'single truth' may be the interpreter's watermark, not the world's.
If the perennial truth is everywhere, why does it always look like the finder?