Introduction: A Question That Is Almost Never Asked
But a fundamental question remains curiously underexplored: how does the system decide which Gospel governs the alignment of the others? In other words, when Eusebius correlates Matthew, Mark, Luke, and John, what determines the direction of comparison? Why is one narrative allowed to stand intact while the others are redistributed, re-keyed, or subordinated?
Eusebius never answers this explicitly. Yet the answer is recoverable, not from later synoptic theory, but from the mechanics of the canons themselves. When examined closely, the Eusebian system presupposes a single narrative axis, and that axis is not Matthew or Luke, but Mark. This conclusion does not depend on modern hypotheses such as Marcan priority. It emerges directly from the way the canon tables function.
What follows is an attempt to show that Eusebius’s system silently but decisively privileges Mark as the backbone Gospel, even while Eusebius himself remains bound to inherited ecclesiastical traditions that prevented him from saying so outright.
Ammonius, Eusebius, and the Problem of Sequence
Eusebius begins his Letter to Carpianus by criticizing the earlier harmony produced by Ammonius of Alexandria. Ammonius, he tells us, placed the corresponding sections of the other Gospels alongside Matthew. The cost of this method was that it “destroyed the sequence of the three Gospels” (τὸν τῆς ἀκολουθίας εἱρμὸν τῶν τριῶν διεφθείρετο). This phrase is more revealing than it first appears.
The destruction of sequence applies to “the three,” not to all four. One Gospel, therefore, is implicitly exempt. In Ammonius’s case, that Gospel was Matthew. Eusebius’s stated improvement is to preserve the body and sequence of the other Gospels while still allowing cross-reference. But what he never states explicitly is which Gospel no longer requires protection because it functions as the structural reference point.
The answer is not supplied by rhetoric, but by outcome. Once the Eusebian tables are constructed, only one Gospel’s narrative order remains untouched across the entire apparatus. That Gospel is Mark.
How the Canon Tables Actually Work
The Eusebian system divides each Gospel into numbered sections and assigns each section to one of ten canons based on how many and which other Gospels contain parallel material. Canon I contains passages shared by all four; Canons II–IV contain passages shared by three; Canons V–IX contain passages shared by two; Canon X contains material unique to a single Gospel.
This description is standard. What is rarely noticed is how these tables behave dynamically when read as a system rather than as static lists.
Across the canon tables, Matthew and Luke are constantly repositioned. Their section numbers jump forward and backward when aligned with Mark. John is redistributed even more dramatically, often detached from chronological sequence entirely. Mark alone moves steadily forward. Its section numbers increase monotonically. There is no instance in which Mark is relocated in order to conform to Matthew or Luke.
This is not accidental. A harmonization system must choose one Gospel whose narrative order it treats as non-negotiable. Eusebius never tells us which one he chose, but the system tells us for him.
Canon II and the Control of the Triple Tradition
Canon II, which aligns Matthew, Mark, and Luke, is the heart of the Eusebian system. This canon corresponds to what modern scholars call the “triple tradition,” and it is here that the controlling role of Mark becomes clearest.
In every Canon II alignment, the Markan pericope defines the unit. Matthew typically expands it; Luke often relocates or paraphrases it. But the boundaries of the episode are set by Mark. This is especially clear in extended narrative sequences such as Mark 8–10, where Mark’s segmentation governs the entire alignment.
Mark chapter 10 is particularly instructive. Every pericope in that chapter is assigned to Canon II. None are treated as unique to Mark. This means that, from Eusebius’s perspective, Mark’s narrative at this point is fully integrated and complete. Matthew and Luke are responding to it, not correcting it.
If Matthew were the base Gospel, we would expect at least some instances in which Matthew and Luke agree against Mark’s sequence or structure. No such instances occur. The absence of a Matthew–Luke corrective layer over Mark is not neutral; it is decisive.
Canon V and the Problem of Matthew–Luke Agreement
Canon V contains material shared by Matthew and Luke but absent from Mark. This canon is often noted but rarely appreciated for its structural implications.
If Matthew were the primary Gospel, Canon V would represent material that Mark omitted or abbreviated. In that case, one would expect the system either to reintegrate this material into Mark’s narrative flow or to treat Mark as deficient. Eusebius does neither. Instead, Canon V is quarantined as a separate block of tradition.
Canon V only makes sense if Mark is already regarded as narratively sufficient. Matthew–Luke agreement is acknowledged, but it is not allowed to reshape the Markan backbone. This is exactly what one would expect if Mark functioned as the base narrative and Matthew and Luke each supplemented it with additional material drawn from other sources.
Mark’s Canon X Material: Residue, Not Innovation
Mark does have unique material, assigned to Canon X. But the nature of that material is crucial. Mark’s unique sections are not theological expansions, clarifications, or doctrinal refinements. They are moments of narrative hesitation, embarrassment, or incompleteness: Jesus’ family thinking he is out of his mind, the two-stage healing at Bethsaida, the young man who flees naked, Jesus’ silent inspection of the temple in Mark 11:11, the abrupt ending at 16:8.
This is not the profile of a later epitomator. A summarizer does not invent unresolved gestures or preserve awkward narrative fragments. These are precisely the kinds of elements later authors smooth out or eliminate. Eusebius isolates them because they cannot be harmonized forward, not because they are secondary.
The Canon X profile of Mark looks exactly like what one would expect from a source text that has been expanded by others, not from a derivative abbreviation.
Why Eusebius Had to Keep Mark Secret
Eusebius was not free to draw the conclusion that his system implies. He inherited from Clement of Alexandria the tradition that the Gospels “with genealogies” were written first, a tradition that assigns chronological priority to Matthew and Luke. He also operated within an ecclesiastical framework that privileged Matthew as the first Gospel in canonical order and liturgical use.
To state explicitly that Mark functioned as the narrative axis would have destabilized both traditions. Instead, Eusebius did something more subtle. He constructed a system that requires Mark to be primary in order to function, while allowing inherited claims about authorship and order to remain formally intact.
The result is a kind of structural disclosure without doctrinal assertion. The canons say what the author cannot.
Conclusion: A Machine That Only Runs One Way
The Eusebian Canon Tables are not neutral. They encode a solution to the synoptic problem centuries before that problem was named. They do so not by argument, but by architecture.
If one attempts to substitute Matthew or Luke as the base narrative, the system breaks down. Canon V becomes unintelligible. Canon II loses coherence. Narrative sequence collapses. Mark’s unique material becomes inexplicable. Only when Mark is treated as the backbone does the entire apparatus function smoothly.
Eusebius did not choose Mark because he wanted to make a theoretical point. He chose Mark because the data forced him to. The canons are a machine, and like any machine, they reveal their assumptions through operation.
What has gone largely unnoticed is that, in building a tool for harmony, Eusebius quietly preserved the strongest ancient evidence for Mark’s narrative priority—not in words, but in structure.
