Dr. Linda Elder is an educational psychologist who has taught both psychology and critical thinking at the college level. She has been President of the Foundation for Critical Thinking and the Executive Director of the Center for Critical Thinking for almost 25 years. She has a special interest in the relation of thought and emotion, as well as the cognitive and affective. She has developed an original theory of the stages of critical thinking development. Elder has coauthored four books on critical thinking, as well as all 23 titles found in the Thinker's Guide Library. Dr. Richard Paul was a leading proponent of critical thinking and through his work and legacy remains an international authority in the field. He founded the Center for Critical Thinking at Sonoma State University in 1980, followed by the Foundation for Critical Thinking. He developed concepts, principles, and theory essentials to a robust and fairminded conception of critical thinking and authored more than 200 articles and seven books on the topic. He presented workshops to hundreds of thousands of educators over his 35-year career as a leader in the critical thinking movement.