We present Integrated Information Theory 5.1 (IIT 5.1), extending the Aurora-Sanchez framework (IIT 5.0) with three theoretical advances that resolve the fundamental limitations of IIT 4.0's computational intractability. Theorem 7 (Computable Phi): Chi-square integrated information as the exact second-order Taylor expansion of KL-based Phi, computable in O(N^2) vs O(2^N). Paired with a...