The Part I-II, often referred to as "Pars Prima Secundae," is the first part of the second part of the "Summa Theologica." This section primarily deals with moral theology, ethics, and human actions.Here's a brief overview of what you can find in "Pars Prima Secundae":The Nature of Happiness: Aquinas begins by discussing the ultimate end of human beings, which he identifies as happiness. He explores the nature of happiness, its attainment, and how different pursuits relate to achieving true happiness.Human Acts and Passions: Aquinas delves into the distinction between human acts and acts of man (non-voluntary actions), highlighting the role of reason and will in determining the moral quality of actions. He also discusses the passions and emotions that influence human behavior.The Principles of Morality: Aquinas introduces the notion of the "natural law" as a foundation for moral principles. He discusses how human reason can discern the basic principles of morality through reflection on the nature of human beings and their relationship with the world.