I used to have a clear and simple idea of sin:
1. Sin is doing what God forbids, or failing to do what he instructs.
2. Sin separates us from God and so is what makes us lost.
3. Sin is willful disobedience to God.
Addressing our problems of sin was equally as straightforward, and corresponds to the previous three statements:
1. Learn what God wills.
2. Receive forgiveness in Jesus.
3. Choose to stop sinning.
Get knowledge, get saved, make new choices. Anyone who suggested anything different was usually seen as "soft" on sin.
Now . . . enter complexity.
Concerning point two, sin does separate us from God . . . sometimes. I say "sometimes" because it is unforgiven sin and an unrepentant attitude that makes sin something that separates us from God. Since God has taken all the necessary action in Christ to forgive our sin, when we are people of faith in the sacrifice of Jesus, our sin (though still here in the old style of life that we all inhabit to some degree) no longer separates us from God. Having been justified, the sin which still needs to be rooted out through sanctification is no longer separating us from God.
Becoming saved and forgiven is extremely easy; how difficult is it to receive a freely given gift that one must only accept?. Having received grace, sin no longer separates us from God (making us lost) but does separate us from the life of God (making us unholy).
Very quickly the "problem" that sins presents to us changes. However, most people seem to think of sin only in the what damns me mode. Sin is exclusively tied to being in a state of lostness, which then gets in the way of dealing with the reality of sin. The old fears of being lost make them grasp for salvation again, rather than resting in salvation and moving toward sanctification.
If the simplistic ideas of point two keep us focused on being saved rather than moving on to maturity, the simplistic idea that sin is wholly a matter of choice puts the final block in the way of growing in holiness. This idea makes being sanctified a stoic endeavor. To overcome sin I need to steel myself to just make better choices.
However, my expereinces show that while there is often willfulness involved in our sinful actions, there are often other factors as well. If it were simply a matter of will, we could always say "Stop it!" and a person could choose to cease committing sin.
Here's where the charges of being "soft" on sin really enter in. If I suggest that besides the will, there are often aspects to sin over which we are powerless to simply "choose" to do differently it sounds like we are absolving people of responsibility. That is not the case.
The assertion that the will is all one needs to eradicate sin is sure to drive people to hopelessness - because when one tries by will alone to deal with sin, and fails, then one often concludes that there is no point in trying. They suppose that they cannot do what they believe others can. They resign themselves to sin, thinking that for some reason of personal failure they can't be sanctified. They hide the sin, and the guilt and shame grow. The sin grows too. And the they continue to be told "just choose to be different, what's wrong with you?
No one tells them that they powerless over sin. No one says that as only God can pronounce justification, only God can work sanctification. No one says that it is not only a matter of one's choice.
Sin is also rooted in the body, which has a willfulness of its own. The desires of our bodies are not always the desires of our spirits. Dealing with sin means that simply having the sincere will of heart might not be enough when the body has other desires. Also there are emotional dimensions to sin and cognitive dimensions as well. We cannot simply will ourselves into new emotions, new thoughts, new actions of the body . . . though willingness of the heart or spirit is essential. Essential but not sufficient. Food is essential to the body for life, but not sufficient for life. Alone, food cannot sustain life. Willingness is essential but not sufficient to lead to sanctification because sin is not simply our unwillingness to follow God.
We are right to call people to will to do good, but the work of overcoming sin is not done in that alone. I am not powerless to will with my spirit, but I am powerless over the emotions and thoughts that come to me. I am not completely powerless with how I will to deal with them, but I cannot control their appearance by all the willpower in the world.
Okay . . . the post is getting too long. But I will continue.