John Stuart Mill 
Utilitarianism [PDF ebook] 

Utilitarianism is philosopher John Stuart Mill’s defense and advocacy of utilitarian ethics. First appearing in three magazine articles, this essay was first gathered into a single book in 1863. While Mill discusses utilitarian ethical principles in some of his other writings such as On Liberty and The Subjection of Women, Utilitarianism is Mill’s only major discussion of the theory’s fundamental grounds.