 Green was perhaps the most important figure within the tradition of British idealism. But the significance of his idealism extends beyond that tradition. His defenses of idealist metaphysics and epistemology and absolute idealism make interesting contributions to an idealist tradition that includes Berkeley, Kant, Fichte, Hegel, and Bradley, among others. His idealist approach to ethics embraces a perfectionist theory of self-realization committed to rich conceptions of freedom and the common good that aims to synthesize the best elements in Greek eudaimonism and Kantian rationalism. Though perfectionism is an underappreciated tradition, Green makes enduring contributions to that tradition. Green’s perfectionism leads him to develop a progressive conception of liberalism that was influential in British politics in the late nineteenth and early twentieth centuries and that bears comparison with contemporary conceptions of liberalism.