On his website, Arminian Perspectives, Ben Henshaw has a questions page at which he answers questions about Arminianism and Calvinism that visitors to his site pose in the comment section of the page. Here is a question from a man named Paul followed by Ben’s answer:
Question: Regarding 1 Corinthians 1:8, “confirm” is future active indicative, which means this is something that is fact and has to come to pass. How is this viewed in light of Arminianism?
Answer: I don’t see a problem with 1 Cor. 1:8. Paul can be using this in a conditional sense in assuming they will continue to believe. In other words, though the end result is guaranteed, it is only guaranteed to those who continue to believe. Also, it should be noted that this can be taken as referring to the church, the corporate body of Christ (as the context would suggest, cf. vs. 2). In that case, the certainty can apply to the corporate body of believers while the individuals’ participation in that certainty is contingent on remaining in that body through faith (cf. Rom. 11 and the imagery of the olive tree, etc.).