Stephen Gilson is a theorist and policy analyst who is best known for his work in disability, diversity, and health policy through the lens of legitimacy theory. Co-authored with Elizabeth DePoy, Gilson developed Explanatory Legitimacy Theory. Through that lens, Gilson analyzes how population group membership is assigned, is based on political purpose, and is met with formal responses that serve both intentionally and unintentionally to perpetuate segregation, economic status quo, and inter-group tension.