Hezser, Catherine. "Oral and Written Communication and Transmission of Knowledge in Ancient Judaism and Christianity." Oral Tradition 25:1 (2010), 75-92.
Hezser notes the relatively difficult means of communication in antiquity compared to today. Written, eyewitness, and in-person communication were certainly available, but could sometimes prove complicated (Hezser 2010, 76). In times of conflict it could even be dangerous to serve as a messenger. Hezser observes that letters of introduction or instruction were considered imporant and fundamental, especially to relationships which cross class boundaries (Hezser 2010, 77).
The New Testament has a relatively limited focus on written texts and letters, normally assuming that writing could be used but that oral messages stood at the center of biblical communication (Hezser 2010, 78). Messages were delivered by going to a person and speaking. However, at the same time, Paul would send letters which were to circulate and reinforce the teaching he engaged in through his personal visits (Hezser 2010, 79). Hezser observes that this pattern of extensive letter writing was continued by Christian leaders as the growth of Christianity continued. She sees it as a means of asserting power and control over far-flung communities (Hezser 2010, 80).
Rabbinic Judaism progressed along similar lines as well. After 70 A.D., Judaism became less centralized, yet developed noteworthy networks of rabbis, who traveled extensively and communicated ideas through letters, which were published and read publicly (Hezser 2010, 81). Because the rabbis typically engaged in the business world, Hezser understands the development of teaching networks as a secondary concern, contrasted with the travels of Christian teachers, which may well have had evangelism as their primary goal (Hezser 2010, 82).
Hezser describes the growth of a mobile and epistolary rabbinic culture, especially in the third tofifth centuries, in some detail, resulting in extensive communication networks as well as written records of decisions and teachings (Hezser 2010, 87). The network among Christian missionaries was also relatively extensive and served to codify doctrines in a consistent way throughout the Mediterranean world (Hezser 2010, 88).