Here's a try to answer the question, "What is a lesson?" It continues the previous discussion of What is Education? and Education Fights Ignorance. a. A lesson consists of observable actions that fit aspects of a describable design consistent with rules people use to learn, such as earning a classic education. b. A lesson changes a behavior pattern of a person. It may be taught by another person; it can be the label given to a change of behavior patterns that occur after a "natural" or contrived event (a dog bites a person, then the person avoids dogs; a flood destroys a valuable painting, so the art collector decides to move from a flood plain: "I learned my lesson about living on a flood plain"). And yes, arguably these descriptions fit lessons in accounts of Socrates teaching on a bench, 21st century classrooms, online curricula, field teaching, open classrooms, Direct Instruction, Direct Learning, etc. How would you describe a lesson differently?