This document summarizes William Perry's theory of intellectual and ethical development. The theory proposes that students progress through 9 positions or stages of cognitive development, from dualistic thinking to relativism and commitment. Perry developed the theory based on interviews with Harvard undergraduates in the 1960s. The theory describes four main positions from dualism to commitment and explains how students' viewpoints change as they progress through college. It has been widely applied to inform instructional strategies and student development programs.