Chapter 55: E₁

The Eight Guarantees (Remark [rem:eight-guarantees-earned], Ch. 74) have been earned. The Global Cartesian Gluing (the relevant theorem, Ch. 75) has been proved. This chapter synthesises. Section 1 identifies what E₁ is: not a model of physics but the structural layer where physics becomes definable. Section 2 presents E₁-complete export contracts to Books IV and V, complementing Chapter 62’s Hinge-perspective contracts with the physics-perspective contracts that the gluing theorem warrants. Section 3 previews the transition to E₂. Section 4 closes Part VIII with a reflection on physics as the first enrichment of mathematics over itself.