Final answer:
Preserving Paul's teachings would have solidified the early Christians in their faith and moral principles, as illustrated by Thecla's devotion to Paul's message. This commitment might have strengthened their position in the face of societal and legal opposition.
Step-by-step explanation:
What would happen if the brethren kept in memory what Paul preached is a question tied to the historical accounts of Paul's ministry and its impact on early Christian communities. If the brethren preserved and adhered to Paul's teachings, they would maintain the doctrines and moral principles that Paul considered essential for salvation, the fear of God, the knowledge of holiness, and the love of truth. In the context provided, Thecla's encounter with Paul's teachings exemplifies how influential his preaching was. The steadfastness of individuals like Thecla who listened to Paul with eager attention illustrates the profound effect that remembering and practicing his teachings could have on the lives of early Christians. On the broader scale, such adherence might have fortified the Christian communities against the societal pressures and legal challenges they faced, much like the trial before the proconsul where Paul defended his teachings as divinely inspired and beneficial for moral guidance and spiritual salvation.