Over the years, as I've read pre-Reformation sources who advocated some form of eternal security, I've noticed that they often cite some of the same Biblical passages advocates of eternal security bring up today. That's significant, given how often critics of eternal security suggest that nobody believed in the concept before the Reformation, that modern interpretations of the relevant Biblical passages are novel and wouldn't have occurred to the pre-Reformation sources, etc. See, for example, my comments in the posts here and here concerning the use of 1 Corinthians 3:11-15 by proponents of eternal security more than a thousand years before the Reformation. In a previous post, I mentioned a book on Gottschalk by Victor Genke and Francis Gumerlock. When I read that book, I repeatedly came across examples of Gottschalk citing certain passages of scripture in the same way or a way significantly similar to how I and other advocates of eternal security interpret those passages (e.g., the citations of John 6:37 and 10:28-29 on page 129, the discussion of Romans 5:9 on page 63 in Gottschalk And A Medieval Predestination Controversy [Milwaukee, Wisconsin: Marquette University Press, 2010]).
Even when a particular Biblical passage isn't brought up, we have indirect evidence for how the passage was interpreted. As I've said before, if a Jehovah's Witness were to interpret a passage of scripture in a manner that contradicts the deity of Christ, we wouldn't need to have an extant document in which Athanasius comments on that passage in order to conclude that he probably didn't view the passage as the Jehovah's Witness does. Since Athanasius affirmed the deity of Christ, we would assume that he didn't interpret the passage as the Jehovah's Witness interprets it. The same principles apply to how scripture was likely interpreted by the people who held to eternal security in the pre-Reformation era.
