St. Thomas Aquinas 
Treatise on Happiness [PDF ebook] 

The Treatise on Happiness and the accompanying Treatise on Human Acts comprise the first twenty-one questions of I-II of the Summa Theologiae. From his careful consideration of what true happiness is, to his comprehensive discussion of how it can be attained, St. Thomas Aquinas offers a challenging and classic statement of the goals of human life, both ultimate and proximate. This translation presents in accurate, consistent, contemporary English the great Christian thinker’s enduring contributions on the subject of man’s happiness.