Final answer:
The question 'why be moral?' references the classic work 'A) The Republic' by Plato. This work examines the nature of justice and morality within society and the individual's role in it.
Step-by-step explanation:
The classic work that is referenced when asking "why be moral?" is A) The Republic by Plato. In this seminal philosophical text, Plato explores the concept of justice and the reasons behind living a moral life. The work is known for its profound impact on philosophy, specifically in discussing the nature of the just society and the moral implications of individual actions within that society. Socrates, the main character in the dialogues written by Plato, investigates these questions through a method that has come to be known as the Socratic method, encouraging readers to examine their own beliefs about morality and justice.
The Republic is not just a work of philosophy but also one of political theory, examining how a society can be organized to reflect justice. Within the text, Plato presents a unified system of ideas, engaging with the most important questions in philosophy, and in doing so, inspires an ongoing debate about the inherent value of living a moral life, beyond the benefits of societal order or personal gain.