Essentialism is an educational theory that believes there is a common core of knowledge that should be provided to all students in order to participate fully in society. It emphasizes a rigorous, teacher-centered approach where students learn established fundamentals through traditional academic subjects like literature, philosophy, science, and mathematics in a systematic way. Essentialists believe education should focus on imparting essential knowledge and developing character, with students trusting the teacher knows best and focusing on learning from them.