The Schrödinger equation is the foundational equation of quantum mechanics — but where does it come from? It is postulated in standard physics, not derived. This paper derives it as the equation of self-referential flow on the 600-cell adjacency spectrum. Below the self-referential threshold φ⁻¹, coherence propagates as a wave satisfying iℏ∂ψ/∂t = Hψ. The imaginary unit i arises from the two-dimensional complex representation (2a eigenspace) of 2I. ℏ is the quantum of action set by the axiom's fixed point. The Schrödinger equation is not a postulate. It is what self-referential dynamics looks like below the confinement threshold.