This text offers an interpretation of John Stuart Mill's ethical theory, Qualitatively-Hedonistic Utilitarianism, as well as a discussion, analysis and solution of problems that have arisen in the theory since the initial publication of Utilitarianism in 1861. Topics discussed include Consequentialism, the Desire Theory of Pleasure, the alleged inconsistency of Qualitative Hedonism, and the relation of Qualitatively-Hedonistic Utilitarianism to Libertarianism...