Logical languages were developed for humans, with the main objective of stating what is a correct argument. Artificial Intelligence (AI) provided a new motivation and application domain for logicians. The main demand of AI to logics is to provide a formal language, a semantics, and a set of proof procedures that allow us to represent the various aspects of knowledge, and to reason about it. AI artifacts, such as robots, agents, “intelligent” programs, etc. act in a (sometimes virtual) world, and take decisions on the basis of what they “know” about this world. Here the need arises to be able to represent and use knowledge. Hence, speaking of Logics for AI largely means speaking of “Knowledge Representation and Reasoning.”