If Mathew was an eyewitness, why would he need to use Mark?

Introduction

A common objection raised in New Testament studies centers on the Synoptic Problem: If Matthew was an apostle and direct eyewitness to the ministry of Jesus, why would he rely so heavily on the Gospel of Mark as a foundational source? To modern readers accustomed to 21st-century copyright and authorship norms, borrowing material might seem like an admission of secondhand knowledge. In the ancient world, however, Matthew’s use of Mark was not a shortcut; it was a deliberate literary, historical, and theological strategy. The Gospel of Mark is essentially the memoirs of the Apostle Peter. Early church fathers, such as Papias (c. 125 AD), recorded that Mark served as Peter’s interpreter and wrote down his preaching accurately.

Peter’s Apostolic Authority

To understand why an eyewitness like Matthew would rely on Mark’s account, one must first recognize the apostolic authority embedded within Mark itself. Far from being a detached, secondary summary, the Gospel of Mark was understood across the early Church as the direct memoirs of the Apostle Peter. As early church historian Papias of Hierapolis recorded around 125 AD, Mark served as Peter’s interpreter, carefully preserving the sermons and recollections of the chief apostle. Peter belonged to Jesus’ innermost circle, witnessing pivotal moments - such as the Transfiguration, the raising of Jairus’ daughter, and the agonizing prayer in Gethsemane - that Matthew himself did not directly see. By incorporating Mark’s text, Matthew was not outsourcing his own memories, but anchoring his Gospel to the foundational preaching of Peter, which was already recognized and revered across early Christian communities.

Ancient Historiography

Furthermore, Matthew’s reliance on an existing framework aligned directly with first-century historiography. In ancient Greek, Roman, and Jewish literature, the goal of a historian was not to present an isolated, novel account, but to demonstrate continuity, consensus, and reliable sourcing. Adopting and expanding upon an established chronicle was considered the gold standard for verifying historical facts. By aligning his narrative sequence with Mark’s widely circulating work, Matthew corroborated the apostolic message, demonstrating to his readers that the testimony of the Twelve was unified and consistent.

A Different Theological Purpose

At the same time, Matthew’s specific audience required a radically different theological and pastoral emphasis. While Mark penned a concise, fast-paced narrative tailored largely for a Roman Gentile readership, Matthew composed his Gospel for Jewish Christians grappling with Mosaic Law, temple traditions, and the Messianic promise. To speak directly to these concerns, Matthew expanded Mark’s skeletal framework with over sixty Old Testament citations to prove Jesus as the promised Davidic King. He integrated extensive blocks of teaching—most famously the Sermon on the Mount—to present Jesus as the New Moses and provide a complete manual for discipleship, while also inserting the legal genealogy of the Messiah and unpacking intricate debates surrounding Torah observance.

Finally, the substantial verbal overlap between Matthew and Mark can also be attributed to a shared, highly structured oral tradition. Prior to the widespread circulation of written scrolls, the apostles spent decades in synagogues and house churches repeating standardized summaries, parables, and sayings of Jesus. In an oral culture practiced in rabbinic memorization techniques, this stabilized reservoir of communal preaching naturally produced parallel wording. This ensured that whether through Mark's parchment or the shared oral catechism of the early Church, the apostolic testimony remained coherent and unified.

TL;DR

Even as an eyewitness, Matthew had clear historical, apostolic, and pastoral reasons to use Mark: 1) Mark preserved the memoirs and preaching of Peter carried immense weight across early churches. 2) In ancient historiography, building upon an existing, credible account demonstrated continuity and apostolic consensus rather than idiosyncratic reporting. 3) Mark wrote a brief narrative for a Gentile audience, whereas Matthew expanded that shared framework for Jewish Christians, adding Jesus' detailed discourses, legal genealogies, and extensive Old Testament fulfillment proofs.

Far from undermining Matthew’s apostolic credibility, his integration of Mark’s Gospel demonstrates the unity of early apostolic preaching. Utilizing Peter’s core memoirs allowed Matthew to anchor his account in the shared testimony of the Twelve, while leaving him ample room to enrich the narrative with the rich Messianic proofs, detailed discourses, and Jewish context essential for his readers.