Artificial Intelligence (AI) is experiencing a period of rapid growth, with the potential for profound impacts on the economy and society at large. The current AI revolution is fueled, in large part, by machine learning. Notably, deep learning has made enormous recent progress on perception tasks from speech recognition to image understanding to biometric security. However, even if machine learning worked as well as it possibly could, AI would not be “solved”. Given a reliable predictive model of a system, one inevitably wants to use this model as a basis for decision-making: that is, for taking action.