The original Greek apologia (ἀπολογία, from ἀπολογέομαι, apologeomai, "speak in return, defend oneself") was a formal verbal defense, either in response to accusation or prosecution in a court of law. The defense of Socrates as presented by Plato and Xenophon was an apologia against charges of "corrupting the young, and … not believing in the gods in whom the city believes, but in other daimonia that are novel".

In later use 'apologia' sometimes took a literary form in early Christian discourse as an example of the integration of educated Christians into the cultural life of the Roman Empire, particularly during the "little peace" of the 3rd century, and of their participation in the Greek intellectual movement broadly known as the Second Sophistic. The Christian apologists of the early Church did not reject Greek philosophy, but attempted to show the positive value of Christianity in dynamic relation to the Greek rationalist tradition.

In the 2nd century, apologetics was a defense or explanation of Christianity, addressed to those standing in opposition and those yet to form an opinion, such as emperors and other authority figures, or potential converts. The earliest martyr narrative has the spokesman for the persecuted present a defense in the apologetic mode: Christianity was a rational religion that worshiped only God, and although Christians were law-abiding citizens willing to honor the emperor, their belief in a single divinity prevented them from taking the loyalty oaths that acknowledged the emperor's divinity.

The apologetic historiography in the Acts of the Apostles presented Christianity as a religious movement at home within the Roman Empire and no threat to it and was a model for the first major historian of the Church, Eusebius. Apologetics might also be directed to Christians already within the community explain their beliefs and justify positions.[8] Origen's apologetic Contra Celsum, for instance, provided a defense against the arguments of a critic dead for decades to provide answers to doubting Christians lacking immediate answers to the questions raised. Apologetic literature was an important medium for the formation of early Christian identity.

In addition to Origen and Tertullian, early Christian apologists include Justin Martyr, Clement of Alexandria, and the author of the Epistle to Diognetus. Augustine of Hippo was a significant apologist of the Patristic era. Some scholars regard apologetics as a distinct literary genre exhibiting commonalities of style and form, content, and strategies of argumentation. Others viewed it as a form of discourse characterized by its tone and purpose.