Book VI, definition 3 of the Elements: a line is cut in extreme and mean ratio when the whole is to the larger segment as the larger is to the smaller. Euclid gives it no special name, no aesthetic claims, nothing mystical, and the recent myth-dispelling literature stresses he treats it as a general ratio. The divine proportion branding arrives with Pacioli's 1509 book of that title, illustrated by Leonardo. The name golden section is German, der goldene Schnitt, early nineteenth century. Phi itself was lettered only in the twentieth.
The canonical claims, the Parthenon's facade, the Great Pyramid, Leonardo's canvases, the ideal face, collapse under measurement: the Parthenon's ratio fits only if you choose convenient edges, and no ancient source mentions proportion-worship. Fechner's 1860s rectangle experiments, the founding evidence that people prefer phi-ish rectangles, do not replicate cleanly. What does hold: phyllotaxis, sunflower and pinecone spirals genuinely count Fibonacci numbers, because that is what efficient packing yields. Nature uses the math; artists mostly use the myth.
The claim: phi's career demonstrates that a number with a beautiful story gets found everywhere, apophenia with a Greek letter, and its believers are running the same pattern-detection this archive files under 11:11 and the Corona cipher: once you know the ratio, the world supplies it. Verdict: the debunk literature says exactly this about the measurement games. But note the twist: the debunkers confirm the spirals. The universe does use phi, quietly, in seed heads. It simply never signed the Parthenon.
If the Parthenon never used it, who needed it to be beautiful?