How did "diversity" come to occupy such a key position in public discourse, particularly concerning education policy? Given the widespread recognition of diversity, is there an intellectual tradition or philosophical orientation that informs its application to education? And, based on the traditions examined, what is gained and lost by focusing on the diversity rationale? This article examines the legal history of using the diversity rationale to justify affirmative action and the philosophical foundation of the ideal of diversity. This foundational analysis not only adds a new direction to the scholarship on the educational benefits of diversity but also illuminates the tensions associated with affirmative action in general and with this rationale in particular. The authors aim to influence educational practice in a direction that well serves a multi-racial/ethnic democratic society. (Contains 8 notes.)