For that which I (old nature) work out, I (new nature) do not experientially know, for that which I (new nature) do not desirously will, this I (old nature) practice, but that which I (new nature) am indifferent to, this I (old nature) do.
The culmination of Paul’s struggle to live out the Christian life by means of law reaches its climax as he describes the inner conflict between his two natures.
On one side is the sin nature, passed down to us from Adam; on the other is the new nature in Christ. Although we are free in Christ from the sin nature that dwells within our flesh, it has not been eradicated. Therefore, the grace believer will experience an ongoing struggle between these two natures, especially when attempting to live by any form of law that provides instruction on what not to do in order to be righteous.
The new nature we have in Christ cannot be corrupted; therefore, it does not possess experiential knowledge of sin. However, since the old nature still resides in our flesh, what is worked out through the flesh is not in accordance with the desires of our new nature. Thus, when seeking to be righteous through the flesh, the sin nature produces what the new nature is indifferent toward.
*Parentheses are used to help distinguish between the two natures to which Paul is referring.