  Part of Robert Batterman’s (1993) discusses problematic definitions of chaos, namely, those that focus on notions of unpredictability. This certainly is neither necessary nor sufficient to distinguish chaos from sheer random behavior. Batterman does not actually specify an alternative definition of chaos. He suggests that exponential instability—the exponential divergence of two trajectories issuing forth from neighboring initial conditions (taken by many as the defining feature of SDIC)—is a necessary condition, but leaves it open as to whether it is sufficient. 