Now then it is no more I that do it, but sin that dwelleth in me.
Paul concluded that the problem of not doing what was right was not the new man in Christ but the sinful, corrupt nature that indwelt him. But we must be careful that we do not excuse our sinning by passing it off to indwelling sin. We are responsible for what we do. All Paul was doing was tracking down the source of his sinful behavior, not excusing it.