Aristotle was Plato's greatest student. One of his big contributions to philosophy was the theory of the four kinds of causes. Ken introduces the guest, Chris Bobonich, professor at Stanford University. Aristotle's ideal state would be ruled by the virtuous citizens. John asks whether that is elitist and Bobonich concedes the point. Aristotle thinks that a state is an association for allowing each citizen to live well. What was Aristotle's notion of friendship? It was broader than our modern notion of friendship. It was closer to the idea of people helping each other be virtuous. 

Aristotle thought the state had a duty to morally improve its citizens. Modern political theorists do not agree. Bobonich argues that Aristotle's notion of a state's purpose is not completely alien to modern minds. Aristotle didn't think that the state should be barred from religion and censorship. 

Aristotle's ethical theory was centered on the question of what kind of life to live. It was not concerned with discovering what actions are right. Why does modern ethical theory differ so much from Aristotle's? Bobonich thinks a lot of the change is due to Judeo-Christian influence. Modern virtue ethics is a revival of Aristotelian ideas about ethics. Aristotle did not think it was possible to specify actions that are always right or always wrong. Aristotle thought that having the virtues was essential to living a happy life.

• Roving Philosophical Reporter (Seek to 04:35): Amy Standen interviews Richard Rubenstein, an Aristotle scholar, about Aristotle's historical influence on ancient Greek, ancient Arab, and medieval European civilizations. 

• Conundrum (Seek to 47:25): Jose from Spain thinks we have a duty to prevent avoidable deaths. This provides an argument for gun control. In turn, it also provides an argument for restricting ownership of cars. Should cars be restricted like guns should be? Is this a good analogy?