This lecture note from a criminal law course introduces fundamental concepts necessary for understanding criminal liability. It explores the purposes of criminal law, including deterrence and retribution, and classifies crimes based on severity and inherent wrongfulness. The note further details the essential elements of a crime, specifically the physical act (actus reus) and the mental state (mens rea), along with principles of causation and concurrence. Finally, it outlines different forms of criminal responsibility, such as accomplice liability and corporate liability, providing a foundational overview for further study of specific offenses.