Description The physics paper ended with thermodynamics as a bridge—the arrow of time (entropy increase) emerges from the spatiotemporal framework, but direction is not causation. This paper begins from the other end of that bridge: the subject exercises negation upon the arrow of time and constructs the law of causality. Dynamics is the fourth-order chisel. The unified principle: the subject does only one thing at every level—negation. The transcendental ground determines the sole self-consistent direction of negation. The construct is the sole self-consistent result of negation operating within the transcendental ground. For dynamics: negation in the arrow of time, within a three-layer transcendental ground (the law of identity + the law of non-contradiction + the spatiotemporal framework), yields the law of causality as the sole self-consistent result. The Nth-order construct requires N chisels from chaos to the current layer, one per layer, in strict order from coarsest to finest—a structural necessity, not a historical contingency. Bridges are bidirectional: forward, remainders emerge from lower orders and provide direction for higher orders; reverse, consequences of negation propagate along the bridge chain from high to low, leaving one layer of consequence at each layer of the transcendental ground. One negation, N-1 bridges, N-1 layers of consequence. Key contributions include: the unified principle of negation across all four orders; the bidirectionality of bridges; the bridge-chain propagation mechanism; the Inheritance Principle; the Inversion Principle (with the discovery that the light cone in the physics paper has no future/past distinction—textbooks project the fourth-order product back into the third-order diagram); the structural death sentence for Laplace's demon; dialogues with Hume, Kant, Russell, Lewis, Pearl, Woodward, and Laplace; the positioning of Pearl's Ladder of Causation within the fourth-order chisel; and eight nontrivial predictions including the structural impossibility of causal-reasoning-based AI exhibiting subjecthood. This paper provides the structural definition of the law of causality—answering a question debated for three hundred years since Hume (1739) without consensus. Fourth paper in the Self-as-an-End Theory Series (Applied Papers: Discipline-Specific Applications). Bilingual: Chinese original with English translation. Related Works Paper 3: "The Complete Self-as-an-End Framework" (DOI: 10.5281/zenodo.18727327) Paper 4: "How Is Subjecthood Possible" (DOI: 10.5281/zenodo.18777364) Series Paper 1 (Philosophy): "Philosophy as Subject-Activity" (DOI: 10.5281/zenodo.18779382) Series Paper 2 (Mathematics): DOI: 10.5281/zenodo.18792945 Series Paper 3 (Physics): "Physics as Third-Order Chisel" (DOI: 10.5281/zenodo.18793538)
Han Qin (Fri,) studied this question.