How can you believe and not believe at the same time? Mark writes about a man who came to Jesus in desperation. His son was possessed by an evil spirit that seemed bent on destroying his precious son.

“Jesus asked the boy’s father, ‘How long has he been like this?’

“ ‘From childhood,’ he answered. ‘It has often thrown him into fire or water to kill him. But if you can do anything, take pity on us and help us.’

“ ‘ “If you can”?’ said Jesus. ‘Everything is possible for him who believes.’

“Immediately the boy’s father exclaimed, ‘I do believe; help me overcome my unbelief!’ ” (Mark 9:21-24).

The old self struggles against the new self

You can pray this man’s prayer every day. You believe, but you are also guilty of unbelief. You see this in yourself when hardship leads you to wonder if God loves you. You see it when you face death and are afraid. You see it when you struggle to overcome a sin in your life and find yourself powerless to make the changes you desire. “Lord, I do believe; help me overcome my unbelief!”

Our good and merciful Father has not left you to face the unbelief of your sinful nature alone. Paul writes: “Therefore, my dear friends, as you have always obeyed—not only in my presence, but now much more in my absence—continue to work out your salvation with fear and trembling, for it is God who works in you to will and to act according to his good purpose” (Philippians 2:12,13). This passage seems to contain a contradiction. First Paul encourages you to work out your salvation. Then he tells you that it is God who works in you both to will and to act.

As long as you keep in mind that you have a new self and an old self, you can understand what Paul is saying. Your new self trusts God and is motivated by God’s love to live according to his will. Your new self desires to hear and learn God’s Word. And your new self always struggles against sin in your life.

However, you never lose your old self entirely. You drown it every day with tears of sorrow and repentance. It is like the crab grass in your garden. You never get rid of it. You just keep pulling weeds to keep them under control. It is the same with keeping your old self under control.

The Holy Spirit helps battle the old self