AI acting systems, or actors – which may be embodied in physical devices such as robots or in abstract procedures such as web-based service agents – require several cognitive functions, three of which are acting, planning, and learning. Acting is more than just the sensory-motor execution of low-level commands: there is a need to decide how to perform a task, given the context and changes in the environment. Planning involves choosing and organizing actions that can achieve a goal and is done using abstract actions that the agent will need to decide how to perform. Learning is important for acquiring knowledge about expected effects, which actions to perform and how to perform them, and how to plan; and acting and planning can be used to aid learning. This chapter introduces the scientific and technical challenges of developing these three cognitive functions and the ethical challenge of doing such development responsibly.