Why is it "σε αυτά", rather than "σε αυτό"? Maybe you can use either?
Yes, you can use either. The plural is more common though, especially when refering to what he says in general. The singular fits only when refering to what he says/said about a particular issue.
I am completely dependent on help from Duo friends to lead me from the fog into the sunshine, thanks
Yes, I also appreciate the help I get from other duolingo users in the languages I study :D