An observation: when Paul wrote his letter to the Galatians in approx. 50AD it was to an already existing church. That is, he was writing to a church which had been formed by Jesus (oral) gospel, and Jesus Spirit. The letter to the Galatians did not form the church in Galatia.
Same with the church on Cyprus….same with the church at Antioch…oh…and same with the church in Jerusalem. When Paul writes to the Galatians later, he is writing to and into a non-textual Christianity, as with his other Letters. He thought such churches to be normative – so do I.