The passage says: And I am sure of this, that he who begana good work in youwill bring it to completion atthe day of Jesus Christ. First, the text does not say: “he who began a good work in anyone”; it says “he who began a good work in you” referring specifically to the saints who were in Philippi at that time.  Second, this verse 6 must be read in context.  Verse 7 says: It is right for me to feel this way about you all, because I hold youin my heart, for you are allpartakers with me of grace,bothin my imprisonment and inthe defence and confirmation of the gospel.Verse 7 reinforces the point that the statement in verse 6 is about those Philippian saints: It is right for me to feel this way about you all.  Notice that verse 7 is the justification for verse 6.If Paul had believed that salvation could never be lost, in verse 7 he would have said quite simply that it was right for him to feel this way because that was the will of God for all.  Paul did not.  Paul said that God would bring the good work he had begun in those Philippian saints to completion because they shared in his imprisonment and in the defence and confirmation of the gospel.  The works of those Philippian saints confirmed to Paul that they have been enduring and holding firm, and so Paul was confident that they would be saved on the day of the Lord.  Note also that as only God is the judge and Paul certainly knew that, Paul was not pronouncing a predictive judgment that those Philippian saints would definitely be saved.  He was merely “confident” that they would be saved i.e. he was clearly just expressing an opinion based on his observation of their works.