The most significant literary work of Plutarch is commonly acknowledged to be the "Parallel Lives," which consists of parallel biographies of pairs of a Greek and a Roman politician or general, numbering 48 in total, of which 46 have survived.

Of course, he also wrote the "Ethics," countless treatises on topics such as virtue, theology, religion, politics, and the role of philosophy in shaping character, mainly of public men, whose choices and actions have always influenced the lives of those being governed.

However, it seems that with his "Ethics," he did not feel he achieved his objective of influencing people of his time and steering them towards the path of virtue, during a period when the Roman Empire was at its peak and heading towards inevitable decline.

Thus, he turned to the biographies of great politicians and generals of the past to provide more tangible and human examples—models to emulate for their great moments or to avoid their unlawful activities.

At the forefront of his choices are Solon with Poplicola, Themistocles with Camillus, Aristides with Cato, Pericles with Fabius Maximus, Alcibiades with Marcellus, Pelopidas with Marcellus, Alexander with Caesar, Agesilaus with Pompey, Demetrius with Antony, and others.

In the "Parallel Lives," Plutarch clearly states that he does not write history nor focus his interest on recording their most notable deeds, but rather through real individuals and true situations, he examines their inner world and provides readers with the necessary historical material to understand the characters of these renowned men and their moral behavior.

Thus, in a masterful way, Plutarch reflects and intertwines the knowledge of the past with the need for moral upliftment of nations and rulers, at a time marked by strong symptoms of decline.