I understand your point, my brother, but to me this is, logically, double speak. To say “keep yourself” only makes sense if there is an imperative, necessary element of the action to be accomplished by us.
But then to say that God himself does the keeping, completely aside of what we do, makes our actions seem irrelevant and unnecessary to accomplish the effect of “keeping”.
To me, you’re thinking completely disregards the sense of contingency in Peter’s language. “If you do these things, you will never stumble” can only mean “if” you don’t do these things, the opposite result will ensue.
Our relationship with God is a synergistic process. When we work in lockstep (Gal 5:25) with God, his power enables us to not stumble, because he keeps us from stumbling. As Peter says, “His divine power has given us everything we need for a godly life through our knowledge of him who called us by his own glory and goodness” (2 Peter 1:3)
God has given us everything that we need, meaning as you say, that it is not our own righteousness or strength that affects the results, but we must avail ourselves of that which is given.
As for the meaning of Jude’s use of ἀπταίστους, Peter uses the same word, though he employs the negative μὴ πταίσητέ instead of the prefix “
a”.
( Jude’s use only occurs once, and Peter’s usage is found five times, three times by James and once each by Paul and Peter.)
The word can mean “I stumble, fall, sin, err, transgress” (Strong), and carries the import of mistakes, human imperfections, deliberate sin, and falling into a place of loss, depending on the context.
Thayer says that one meaning is “b. to fall into misery, become wretched (often so in Greek writings): of the loss of salvation,
2 Peter 1:10.”
That Jude says God is “able” does not technically mean that it will necessarily happen, but only that it can! For instance, God is able to save, and will save- if and when we believe. Thus, He is able to keep us from πταίω, “if we do these things”, that is, if we add to our faith “in increasing measure” everything his power has given to us to be godly.
Jesus is the Author and Finisher of our faith, but we must fix our eyes upon him to experience his finishing. (Heb 12:2)
Doug