This text, excerpted from "Ethics 101" by Brian Boone, examines various ethical theories and their practical applications. It explores the historical development of ethical thought from ancient Greek philosophers like Socrates, Plato, and Aristotle, to later thinkers like Immanuel Kant, John Stuart Mill, and Friedrich Nietzsche. The author analyzes key concepts in different ethical frameworks such as deontology, utilitarianism, virtue ethics, and existentialism. He also presents real-world scenarios and thought experiments, like the trolley dilemma and the prisoner's dilemma, to illustrate the practical implications of these theories. The text concludes by discussing applied ethics in various fields such as business, politics, and medicine.