Laws of Social Evolution: A Unified Dynamic Equation of Historical Bias, Sedimentation Inertia, and Disturbance

History is neither a random walk nor a linear progression, but exhibits structured trajectories: certain civilizations cycle repeatedly between the same institutional forms, certain societies consistently return to similar states after external shocks, and the characteristics of dead civilizations persistently resurface in their successors. What is the common source of these regularities? This chapter provides a unified dynamic equation for social evolution within a sedimentation field dynamics framework: dCore_S/dt = f(current dynamic pressure) + historical residual bias × bias strength + disturbance term. History is not random because the historical residual bias term is nonzero; history is not deterministic because the disturbance term and current dynamics coexist. From this, four laws of social evolution are derived: the Path Dependence Law (historical starting points determine long-run trajectories), the Evolutionary Inertia Law (why core structures resist complete replacement after revolutions), the Evolutionary Convergence Law (why industrialization, bureaucratization, and marketization emerge across civilizations), and the Evolutionary Bifurcation Law (why societies split into multiple trajectories under critical pressure). Three results follow. First, the four laws correspond to four distinct observable historical patterns and are mutually consistent. Second, the laws of social evolution are the social-layer realization of field evolution laws, inheriting the dynamic framework of field theory rather than introducing independent assumptions. Third, evolutionary trajectories carry no directional purpose — the dynamic equation describes only direction and speed, not the value of the destination.