Pietas

Cicero defined pietas as the virtue "which admonishes us to do our duty to our country or our parents or other blood relations." The man who possessed pietas "performed all his duties towards the deity and his fellow human beings fully and in every respect," as the 19th-century classical scholar Georg Wissowa described it. Cicero suggests people should have awareness of their own honor and must always attempt to raise the honor of others with dignified praise. Furthermore, praise, admiration, and honored actions must be beyond all one's own desires, and actions and words must be chosen with respect to friends, colleagues, family, or blood relations. Cicero describes youth in the pursuit of honour: “How they yearn for praise! What labours will they not undertake to stand fast among their peers! How will they remember those who have shown them kindness and how eager to repay it!”

The first recorded use of pietas in English occurs in Anselm Bayly's The Alliance of Music, Poetry, and Oratory, published in 1789.

As virtue

Pietas erga parentes ("pietas toward one's parents") was one of the most important aspects of demonstrating virtue. Pius as a cognomen originated as way to mark a person as especially "pious" in this sense: announcing one's personal pietas through official nomenclature seems to have been an innovation of the late Republic, when Quintus Caecilius Metellus Pius claimed it for his efforts to have his father, Numidicus, recalled from exile. Pietas extended also toward "parents" in the sense of "ancestors," and was one of the basic principles of Roman tradition, as expressed by the care of the dead.

Pietas as a virtue resided within a person, in contrast to a virtue or gift such as Victoria, which was given by the gods. Pietas, however, allowed a person to recognize the divine source of benefits conferred.

A Roman with the virtue of pietas did not leave his religious duties at the door of the temple, but carried them with him everywhere, following the will of the gods in his business transactions and everyday life.

— Max Pfingsten

Pietas held great importance in the realm of international relations and diplomacy. The credibility of a commander relied heavily on their willingness to set aside personal gain and fully dedicate themselves to a cause, refraining from any treacherous actions. This emphasis on credibility led to the reputation of individual commanders and the Roman state itself playing a pragmatic role in negotiations and discussions. Commanders' commitment to fides needed to be consistent, demonstrating credibility through ongoing actions and a steady approach in dealings with neighboring entities. Upholding respect for existing contracts meant honoring pledges and oaths, thus reinforcing Rome's commitment to ethical behavior and the continuation of diplomatic strategies. The chances of resolving conflicts were minimal if deceit became the standard in negotiations by commanders.