I think if you review the discussion you'll see I've tried to stay focused on the original question to Forest Keeper:
"Can only saved Christians can choose to do good?"
I would suggest going back and reading through the posts. We have gone from knowledge to good works to good decisions. These are all different things and require different responses. When you stated "choose to do good" this implies that can Christians choose to do good [works].
People do not have good "knowledge" which I stated sounded very Gnostic and was condemned by the early Church as heresy. Nor can people make alway make good decisions; Adam found that out even being perfect. As far as works, I posted what the Confessions state.