What is the Letter to Diognetus?

TL;DR:

The Letter to Diognetus is an early Christian apologetic work that explains and defends the faith, emphasizing the distinctiveness and moral integrity of believers. The Letter to Diognetus encourages Christians to live faithfully and lovingly in the world as a testimony to God’s transforming power.

what does the bible say?

The Letter to Diognetus, also sometimes referred to as The Epistle of Mathetes to Diognetus, is a letter defending the Christian faith. Believed to have been written between AD 130 and AD 180, this letter is possibly the earliest example of Christian apologetics, which is the exercise of using reasoned arguments to defend Christian belief and practice. The letter was found in a thirteenth century codex ascribed to Justin Martyr and first published in 1592. Because of its reasoned defense of Christianity, many transcripts of the letter were made, which is fortunate because the original was destroyed in a fire in 1870 during the Franco-Prussian War.

The Letter to Diognetus provides one of the earliest systematic defenses of the Christian faith, illustrating how believers explained and lived out their beliefs in a largely pagan world. It is not inspired Scripture, but it echoes principles of God’s Word. For instance, it discusses the irrationality of idolatry (Exodus 20:3-6; Isaiah 44:9-20). Additionally, the Letter also discusses God’s Holiness and the set-apart life of believers (Leviticus 21:8; John 17:14). This theme of the separateness of believers is manifested in the Old Testament through the Mosaic Law, which distinguished Israel from the pagan nations around them (Deuteronomy 7:6) and pointed to a greater spiritual separateness through Christ (Hebrews 10:1). The theme is present in the New Testament through the love shown in the transformed life of the Christian (John 13:34-35; 2 Corinthians 5:17). The Letter offers insight into the moral distinctiveness, devotion, and community life of early Christians and serves as both a historical document and a model for engaging others with the truth of the gospel.

from the old testament

The Old Testament does not mention the Letter to Diognetus, as it was written centuries later. However, the Old Testament provides foundational principles that shape Christian apologetics, such as the irrationality of idol worship the prophet presents in Isaiah 44. In that chapter, Isaiah describes how illogical it is for people to chop down a tree, form an idol from it, and use the rest of the wood to make a fire. In other words, it’s illogical to worship something that we make.
God’s holiness, His covenant relationship with His people, and His call for His followers to live distinct lives set apart for Him (Leviticus 11:44-45; Deuteronomy 6:5-6) are also emphasized in the Letter to Diognetus. Early Christians drew on these themes to explain how faith in God was expressed through Jesus Christ.

from the new testament

The New Testament emphasizes the same ideas expressed in the Letter to Diognetus: the distinctiveness of Christians in society, the transformative power of faith in Christ, and the calling to live godly lives while surrounded by non-believers (John 17:14-16; 1 Peter 2:11-12).
Like the Letter to Diognetus, the New Testament encourages Christians to demonstrate their faith through love, moral integrity, and devotion to God, providing a framework for explaining Christianity to outsiders (John 13:34-35; 1 Peter 2:11-12; Colossians 3:12-14).
Chapters three and four of the Letter to Diognetus echo many New Testament passages about the futility of our works to save us; only Jesus saves. For instance, Paul wrote to the Galatians, “yet we know that a person is not justified by works of the law but through faith in Jesus Christ, so we also have believed in Christ Jesus, in order to be justified by faith in Christ and not by works of the law, because by works of the law no one will be justified” (Galatians 2:16).

implications for today

The Greek writer and recipient of the Letter to Diognetus are unknown; mathetes means "student" or "disciple" and diognetus means "God-born." The writer claims to be a disciple of the apostles and uses language consistent with an ancient Christian community known as Johannine Christians who emphasized the apostle John's teachings. The recipient being addressed as "God-born" is also consistent with John's teaching that those who believe are "born of God" (John 1:12-13; 1 John 3:9; 4:7; 5:1, 4, 18). However, three men named Diognetus during that time period could have been the intended recipient. One man was a procurator in Alexandria around AD 200 and the other two men were part of an aristocratic family who served on the city council in Smyrna during the time of Polycarp.

The Letter to Diognetus has twelve sections or chapters that build a logical argument as to why its recipient should reject other religions and join Christianity instead. It includes arguments about the foolishness of worshipping manmade gods in the Greek way, the futility of Jews’ works-based attempt at righteousness, the separateness of the Christian life, and several other arguments for Christianity.

The Letter to Diognetus shows that people have been curious about the Christian faith and have asked intriguing questions since Jesus' disciples spread the gospel far and wide. It provides an example of how to lovingly engage those who do not yet believe and invite them to make this faith their own. It also demonstrates the importance for Christians to live out their faith in ways that the community around them can recognize as empowered by a sovereign and loving God. May we join Mathetes in his hope that non-believers will be convinced to personally experience knowing God.

understand

The Letter to Diognetus (AD 130-180) is an early Christian apologetic defending the faith and explaining that Christians live morally distinct lives.
The Letter emphasizes love, devotion, and the transformative impact of faith.
The Letter to Diognetus also systematically addresses questions about Christianity, contrasts it with other religions, and invites readers to experience God’s salvation.

reflect

How does the example of Christians living distinct, loving lives challenge you to reflect Christ in your life?
How can you imitate God’s kindness and devotion as described in the Letter to Diognetus?
How does knowing that early Christians thoughtfully defended their faith inspire you to share your faith with others?

engage

Why is it important that believers’ lives visibly demonstrate the transformative power of faith to non-believers?
What strategies from the Letter to Diognetus can help us engage thoughtfully and lovingly with people who question or misunderstand Christianity?
How does contrasting Christian living with surrounding cultural or religious practices help us and others understand the distinctiveness of our faith?