Stable or Robust? What’s the Difference?

Exploring the difference between "stable" and "robust" touches on essentially every aspect of what we instinctively find interesting about robustness in natural, engineering, and social systems. It is argued here that robustness is a measure of feature persistence in systems that compels us to focus on perturbations, and often assemblages of perturbations, qualitatively different in nature from those addressed by stability theory. Moreover, to address feature persistence under these sorts of perturbations, we are naturally led to study issues including: the coupling of dynamics with organizational architecture, implicit assumptions of the environment, the role of a system's evolutionary history in determining its current state and, thereby, its future state, the sense in which robustness characterizes the fitness of the set of "strategic options" open to the system; the capability of the system to switch among multiple functionalities; and the incorporation of mechanisms for learning, problem solving, and creativity.