Book 3 takes Hume's principles of pride, humility, love, and hate from Book 2 and uses them as the foundation for morality of natural and artificial virtues and vices. This includes the foundation of justice, property, beauty, and utility. Hume also explains the obligation of contracts and why governments are not based on any social contract.
Juan is the founder of Superphysics, derived entirely from Adam Smith and David Hume. http://superphysics.one