Paul says plainly at
Galatians 1:11 that he never met an historical Jesus and was never instructed about him by other people. Instead he had a vision ─ that is, everything Paul tells you about Jesus comes out of his own head.
Your description of Paul is very flattering, as it makes him look like the exceptional genius who came up with an entire religion. The truth is far more prosaic.
There are no Pauline scholars of note, whom I am aware of, that would endorse your contention that "
everything" Paul tells us about Jesus "
came out of his own head".
The consensus (here I am with scholarly consensuses again), typified by the likes of Paula Fredriksen, E.P Sanders and the late Larry Hurtado, is that the extent of the novelty of Paul's theology in the early church has been
greatly exaggerated in the traditional accounts - not entirely so, since he was (in many respects) an exceptional thinker in the early church and seems to have pursued a more radical doctrine of grace/antinomianism, but in the main he was not innovating.
There wasn't even much of a divide between himself and James, Jesus's brother (referred to twice by Josephus, on both occasions almost universally accepted by scholars as authentically Josephan), the leader of the early church, as has been commonly opposed - or else he wouldn't have urged his followers to pay the voluntary tithe/collection for James:
"From the beginning—before Paul was even involved—the movement had admitted gentiles without requiring them to be circumcised. James, Peter, and John all affirmed that position, back in Jerusalem...And finally, Paul, as we have seen, worked in concert with James about the collection for the Jerusalem community throughout the rest of his missions. No ideological breach yawned between the two men" (Paula Fredriksen (2018), p.188).
Paul's Gentile churches were literally financing James's Jerusalem church. As the Fordham historian L.L. Welborn has noted in a Cambridge University Press study from 2013:
https://www.cambridge.org/core/serv...texts_and_consequences_of_a_pauline_ideal.pdf
In Corinthians, Paul stipulates as the criterion and goal of the collection for the poor saints in Jerusalem the ideal of ‘equality’ (ἰσότηϛ): ‘for the purpose [of the collection] is not that there [should be] relief for others and affliction for you, but rather [it should be] out of equality (ἐξ ἰσότητοϛ). In the now time, your abundance should supply their lack, in order that their abundance may supply your lack, so that there may be equality (ὅπωϛ γένηται ἰσότηϛ)....
Paul’s appeal to ‘equality’ as the principle that should govern relations between Greeks and Jews would be especially shocking, if Hans Dieter Betz is correct in his interpretation of Paul’s subsequent statement in Corinthians about the effect of the collection as signifying the obligatory submission of the Achaians to the Jerusalemites
We now know with relative certitude, based upon ample textual studies - as you allude to yourself - that in Corinthians, Galatians and Philippians he references pre-Pauline hymns and creedal statements. The famous statement: "
There is neither Jew nor Gentile, neither slave nor free, nor is there male and female, for you are all one in Christ Jesus" (
Galatians 3:28), has for now long been regarded by most scholars as a pre-Pauline baptismal formula. In other words, he didn't actually 'come up' with that profound insight - he simply inherited it from the Jerusalem church and was referencing what, by then in the 50s CE, was a common aphorism among the nascent communities of Jesus-believers used in their rituals.
Paul refers to his conversations with people who knew Jesus directly, including his brother James, the apostles Peter, John and others. He lived with the apostle Peter (Cephas) for fifteen days and we know that they were close enough to have engaged in a very heated argument that Paul boasted about many years after the fact. In both
Galatians 1:18-9 and
1 Corinthians 9:5 the “
brothers of the Lord” are mentioned. The existence of Jesus’ brother James is further strengthened by the fact he is attested outside of Christian texts – in Josephus,
Antiquities of the Jews, XX.200-203, where he is described as well-liked notable of Jerusalem whose stoning to death by the chief priests sparked outrage.
In the early Christian movement, "prophecy" and private "revelation" were signifiers of authority.
The Didache, the earliest extra-canonical (first century) catechism of Jewish Christianity, states: "
Let every prophet who cometh unto you be received as the Lord".
The early church was a movement that literally thought it was living in the messianic times predicted by the Hebrew prophet Joel: "
And it shall come to pass afterward, that I will pour out my Spirit on all flesh; your sons and your daughters shall prophesy" (Joel 2:28). As such, its not surprising that early Christians all tried to "upstage" one another by claiming that they too had been 'gifted' with mystical revelation or a vision of the Lord, as the Holy Spirit was believed now to be dwelling within all followers of Jesus.
When Paul boasts in Galatians that he received revelations unmediated through human knowledge, it needs to be understood in this context. He wasn't saying anything that was exceptional in the Christian movement - and his hyperbole doesn't actually mean that
everything he's telling us about Jesus was derived from visions, a ludicrous conclusion because its flatly contradicted by the numerous occasions in which he cites the
oral traditions.
You're taking his self-propaganda far too seriously there.
Paul was not writing a biography of Jesus, nor was he interested in doing so. He was writing letters to churches he had founded in an attempt to ensure that they overcame factionalism, were thriving and growing, by pushing his understanding of the Jesus movement.
What's fascinating, is that in spite of this agenda we find a number of references to various elements of Jesus's life and preaching in his letters (which are 'common knowledge' to the audience in the 50s A.D.), which indicates that Paul knew a lot more than he wrote down.
Firstly, we learn from
2 Corinthians 10:1 that Paul appealed to his readers by the,
"meekness and gentleness of Christ". As a number of scholars have noted: "
On a number of occasions Paul appealed to the example of Christ and urged others to imitation. For example, he encouraged the Philippians to have the mind of Christ in humility and service (Phil 2:5-11). Elsewhere he instructed the Romans to put on the Lord Jesus Christ and avoid self-gratification (Rom 13:14). In the midst of Jewish-Gentile discord in the Roman church, Paul told them to welcome each other as Christ has welcomed them (Rom 15:7). The apostle even urged the Corinthians to imitate him since he imitated Christ (1 Cor 11:1). Admonitions to imitate Christ depend ultimately on having authentic traditions regarding Christ’s life. The traditions about how Christ lived would have provided a script for imitation. When, for example, Paul taught the Romans to strive to please their neighbors, he appealed to Christ’s example: “for Christ did not seek to please himself” (Rom 15:3)." (
Encyclopedia of the Historical Jesus, ed. Craig A. Evans, Routledge (2008)). Other examples:
1 Corinthians 15:1-8. Paul tells us he received the tradition (
paredōka = “I delivered”;
parelabon = “I received”), of Christ’s death on a Roman execution stake and burial. He reiterates this in 1 Cor. 2:2, Gal. 3:1, 2 Cor. 13:4, and many more occasions. He didn't derive this from a "revelation" but from the same synoptic tradition we find in the gospels.
1 Corinthians 11:23-26 Paul tells us that he received the tradition that Jesus had a last supper with his disciples before dying, quotes his alleged words "this is my body...blood...do this in memory of me") and then notes that he was betrayed by one of his disciples. Again, no personal revelation involved here - just a historical memory distributed in the early movement that formed part of the verbal tradition that was eventually written down in Mark's gospel.
1 Corinthians 15:3-8 Paul tells us that Jesus had a core of inner disciples called "
the Twelve". Again, no revelation involved here - just an allusion to another verbal tradition.
Romans 1:3 Paul tells us that in "
his earthly life [Jesus] was a descendant of David". That is, he tells us about Jesus's flesh and blood ancestry (this could
only have come from a family tradition i.e. "do you know, our family is supposedly descended from King David").
1 Thessalonians. 2:14–15 Paul tells us that Jewish leaders (the High Priests) participated in the killing of Jesus, again that's a reflection of the synoptic tradition of the trial before the Jewish elders.
Then we have quotations of Jesus's teachings in Paul's epistles. In answering the Corinthians' questions about marriage, Paul cites Jesus' ruling on divorce as binding on his followers. "
To the married I say, not I but the Lord, that the wife should not separate from her husband but if she does, let her remain single or else be reconciled to her husband and that the husband should not divorce his wife" (
1 Corinthians vii. 10 f.).
You can find this exact same teaching against divorce in Matthew and Luke - Paul didn't "come up with it" by himself.
Paul tells the Corinthians that "
the Lord [Jesus] commanded that those who proclaim the gospel should get their living by the gospel" (
1 Corinthians ix. 14). This "command" appears in our synoptic tradition in the Matthaean commission to the twelve (Matthew x. 10), "
the labourer deserves his food", and in the Lukan commission to the seventy (Luke x. 7).
As Bart Ehrman notes, "
Paul's first letter (1 Thessalonians) is usually dated to 49 CE; his last (Romans?) to some twelve or thirteen years after that [...] In addition to data about Jesus’s life and death, Paul mentions on several occasions the teachings he delivered. Where did Paul get all this received tradition, from whom, and most important, when? Paul himself gives us some hints. He tells us, he made a trip to Jerusalem, and there he spent fifteen days with Cephas [Peter] and James. Cephas [Peter] was one of Jesus’s twelve disciples, and James was his brother."
Scholars can discern strong 'kernels' of early Palestinian Jesus tradition through multiple attestation, criterion of embarrassment and many other analytical tools - and Paul has been found to exhibit this.
Thus, to say that "
everything" he tells us about Jesus is from his own head is extremely far off-the-mark.