The believer’s spiritual battle with indwelling sin has caused great confusion in the Church. Many think of this conflict as the Old Man versus the New Man, and describe it as a fight between two dogs. The black dog represents sin, the white dog represents holiness, and the dog that prevails is the one that you feed.

While Christians should certainly be engaged in struggle with sin, the truth is that we have only one nature, not two. Believers have been born again, and given new life in Christ. As John Owen rightly points out, our battle is with the remaining principle of sin within us, the enmity in our flesh which wages war with our soul. The battle for purity must abolish the principle of sin which remains, or we will find our flesh warring against God.

Our journey begins by understanding that within our fallen humanity we have an enmity which sets its affections against the things of God. We who have had our nature changed by God, who live in newness of life in Christ, still have the principle of sin living within our flesh. We are told by Paul to walk by the Spirit so that we will not fulfill the desires of the flesh (Gal 5:16). We are encouraged to make no provisions for the flesh in regards for its lusts (Rom 13:14) because those lusts wage war with the soul (1 Pet 2:11).

Owen reminds us that if we fail to war against sin, the enmity of sin will war in us and move us away from God. He points out that we are moved away first in our affections, then in our mind, and finally in our practices. Sin will cause us to no longer desire the things of God, to dwell on ungodly things, and eventually to act according to its lusts. Sin is an aversion to all the things of God, and is utterly contrary to Him and the new nature He has given us.

Sin is not a principle to be trifled with. It is to be mortified. Owen describes the dangers of sin when he says, “Enmity may lose some of its effectiveness, but – like every drop of poison – it will infest and spread its poison again” pp 15-16.

After finding such a principle of sin living within, we must be prepared to do all that is necessary to gain mastery over the flesh. This will not be achieved by wishful thinking, halfhearted effort, or self-willed determination. Rather, spiritual battles are won by:

1. Fixing our affections on God
2. Laboring to give no room for ungodly affections
3. Not allowing sin to gain victory
4. Reflecting continually on how contrary sin is to our new spiritual nature
5. Striving to possess the mind which delights in the greatness of spiritual truth

This conflict is a real and expected part of the Christian life. Don’t be surprised or dismayed that pursuing Christ should be so difficult, but instead consider it a privilege to take up the fight against ungodliness within. As Owen says, “Grace changes the nature of a man but nothing changes the nature of sin” (p 16). Make no provision for the flesh in regards to its lusts (Rom 13:14), for it is sin which could master me (Rom 6:14). Jesus has come to set us free from the power of sin (Rom 6:1-2). Now is the time for us to live like it.