We prove that neutrinos cannot have mass. The proof requires no new mathematics. The Feigenbaum Domain Theorem — derived from universality results established by Feigenbaum (1978) and Lanford (1982) — shows that no scalar coupling survives a complete cascade transit unchanged. The Higgs mechanism generates fermion mass through scalar coupling. A particle that never crosses the decoherence threshold cannot acquire Higgs mass. This is a structural mathematical result, independent of any model assumption. Neutrinos are permanently pre-decoherent cascade particles. They transit the cascade energy staircase E_n = v/δⁿ without ever completing the emergence that would constitute mass. The apparent flavor change that oscillation experiments detect is not interference between mass eigenstates. It is phase drag across cascade regime boundaries, governed by the ghost coupling g(n) = (α−1)/δⁿ, where (α−1) = 1.5029 is the first bifurcation increment of the cascade. This mechanism reproduces three independent observational facts without mass as an input: the PMNS mixing angles sin²θ₂₃ = 0.57296 [0.167%] and sin²θ₁₂ = 0.30151 [0.491%]; the ratio of apparent mass-squared differences Δm²₃₂/Δm²₂₁ = δ²(α−1) = 32.76, versus the measured 32.56 [0.6%]; and the pattern of near-maximal mixing explained by the cascade T-regime (T = δ/α = 1.865). The 2015 Nobel Prize correctly identified that neutrino flavor change occurs. The conclusion that flavor change requires mass was the only interpretation available at the time. Accepted mathematics now establishes that for a permanently pre-decoherent particle, mass is not merely unnecessary. It is forbidden. The neutrino does not oscillate. It transits. The riddle is solved.