Darren Slade, PhD in theology and church history, writes, “In AD 125, Roman Emperor Hadrian (AD 117–138) traveled to Athens for the Eleusinian mysteries. According to Eusebius (ca. AD 265–339), a Christian philosopher named Aristides produced apologetic books for the Emperor. His apologetics compelled Hadrian to counter the arbitrary prosecution of Christians (Chron. 2141–42; Hist. eccl. 4.3.3). Though not the first apologist, Aristides produced the earliest extant apology in church history (cf. the fragment from Quadratus, Hist. eccl. 4.3.2), which helped to make Christian apologetics a distinct genre. Unfortunately, no document references Aristides prior to Eusebius (Chron. 2141), who described him as a faithful Athenian earnestly devoted to Christianity (Hist. eccl. 4.3.3). Jerome (ca. 347–419) later implied that Aristides was a philosopher before his conversion and that the apology testifies to his brilliant eloquence (Vir. ill. 20; Epist. 70.4). Similar to Justin Martyr, Athenagoras, and Tertullian, Aristides retained his philosophical background while discussing Christianity.“

Aristides of Athens wrote his apology to the emperor Hadrian. He is the earliest extant apologist whose writings survive. His apology’s primary argument was the assertion that Christians were the Empire’s superior citizens. He begins with an argument from beauty (aesthetics) for the existence of God (“when I had considered the heaven and the earth and the seas, and had surveyed the sun and the rest of creation, I marvelled at the beauty of the world”) and subsequently moves to a form of cosmological argument from motion. He identifies 4 classes of humans: barbarians, Jews, Greeks & Christians. Christians are seen as a new type of humanity where natural ethnicity continued but are a new type of people in Christ. He appeals to the superiority of Christians by their superior morals (an appeal to Christian ethics.) There is also an appeal to corpus writings of Christians (indicating there were identifiable inspired writings as early as 125 AD.) There is a warning of eschatological judgment to come. Repentance is required and he calls the emperor himself to repentance.

Aristides is a great place to start educating oneself on the early apologists. You can read the Apology of Aristides here or buy a copy from Amazon here.