Regardless of content area, helping students develop critical thinking skills is one of the most important things teachers do. Dr. Joe Lau, Professor of Philosophy at Hong Kong University has developed an Open Courseware program full of resources for teaching and developing critical thinking skills. Dr. Lau’s Critical Thinking web has games, puzzles, and quizzes in addition to lecture notes and links to additional resources. The page on evaluating arguments presents many diagrams and activities designed to help visitors recognize valid arguments and invalid arguments.