This paper develops a purely structural analysis of dynamical emergence on compact, one-parameter constraint manifolds with involutive symmetry. Using a conserved binary partition as a canonical example, it establishes three general results: (i) all symmetry-invariant observables are stationary at the fixed point of the involution, implying that flat points are maximally symmetric but dynamically silent; (ii) nonzero first derivatives (slope) constitute the minimal geometric requirement for distinguishability, preferred direction, and moduli-space dynamics; and (iii) second derivatives (curvature) govern the survivability of structure, with large curvature producing tidal instability and minimal curvature defining a finite corridor of persistent dynamics. The constraint manifold is shown to be a Thales semicircle, whose induced metric yields a hyperbolic (Poincaré) geometry. Promoting the flat proto-metric to this induced metric introduces a nontrivial connection that generates restoring behavior, boundary protection, and geometric deceleration without invoking additional forces or dynamics. The resulting Thales Lagrangian demonstrates how geometry itself participates in evolution, reproducing the transition from purely potential-driven motion to geometry-assisted dynamics in a manner structurally analogous to the Newtonian–Einsteinian progression. These features are shown to be shared by string-theoretic moduli spaces with duality symmetries (T-duality and S-duality), entropy landscapes, and constrained information-theoretic systems. The work makes no microscopic or phenomenological claims; its contribution is kinematic and geometric. Flatness, slope, and curvature are identified as universal structural primitives governing when dynamics can exist, how it emerges, and where it remains stable.