We can see clear instances where diverse Christians agreed on what they were teaching about Jesus's miracles, teachings, and other biographical information.
This helps because examples are one of the most straightforward ways to establish the point. At the same time, we do not see clear counter-examples to the thesis that Christians largely agreed on Jesus-biography.
In general, Christian churches in AD 30-70 were basically unified; they agreeed with respect to who their leaders were, what their doctrine was, and what the history (with Jesus) looked like.
See this page to explore six arguments:
This is relevant because if they were unified in general, then we can expect them to be unified on the basic teachings regarding what Jesus did and taught.
The four Gospels regularly report on the same basic incidents (e.g. Jesus's crucifixion), and yet despite an abundance of opportunities the Gospels seem to never (or virtually never) yield actual contradictions. This is what we would expect of Christians if they were largely unified on what they said about Jesus, but it is quite surprising if Christians were not unified.
We see that Gospel traditions (stories) independently attest to much of the same Jesus-biography.
A full page at /gospel-stories/spew/independently-attested-events will discuss these arguments:
This is relevant because it would be the central test and example when looking to see if Christians were in fact unified or not on what they were saying about the historical Jesus's life and deeds. If we looked and saw diversity among the historical traditions then the thesis of unity would be falsified, and there were many opportunities to see this. Instead, this constitutes a strong confirmation of the opposite: they were unified indeed.
Christians were quite learned when it came to the details of Jesus's ministry, life, teachings, sayings, and deeds.
A page will discuss these arguments:
This helps show that Christians were largely unified because knowledge is factive (i.e. accurate), and if they all have accurate beliefs concerning the outlines and details of Jesus's life and ministry, then they would all believe the same basic things.