The Flesh and Demons: They work together!
Many who criticize the deliverance ministry will claim that we tend to blame everything on demons to avoid personal responsibility. That is simply not true in most cases in this type of ministry. I do not intend on ignoring the flesh or overemphasizing the demonic, but I would like to clearly explain how the two work together to carry out Satan's plan in our lives.
The flesh is the gateway to the demonic. Many times (unless it is generational, etc.), it is through the flesh that demons gain entrance into a person's life. We are first tempted by demons (the enemy works through his army of fallen angels) because they are seeking to gain entrance into our lives or carry out a plan to kill, steal or destroy us (see John 10:10), then once we give in, they become welcomed into our lives, and once they enter, they will serve as bad friends who will constantly seek to negatively influence us. Having a spirit of lust will be like working in an adult bookstore... it will work to wear you down and get you to give in. Without having that spirit, it is much easier to resist the temptation. But wait a minute, what about plain old temptation that is thrown our way on regular bases? We are not immune from that, are we? No, unfortunately we will probably be tempted to a certain degree until we leave this earth. But let me illustrate the difference between normal temptation and having a demon which is pressuring you to sin: When you drive down the road and see an adult bookstore alongside the road, you can easily resist thinking about what is inside that store... that is temptation. Now let's say that you had to work in such a store, and have sex videos playing on the TV screens all day long... that is what it's like to have a spirit of lust. There is a VERY big difference! If you simply feel a little temptation once in a while and find it very easy to resist, then you are likely experiencing simple temptation from the enemy and your goal is to resist it and move on. However, if you feel driven to lust or pornography (or other sinful behavior such as anger, hate, rage, etc.), then you likely have a spirit that must be driven out.
As I said earlier, the flesh is the gateway to the demonic. Demons cannot simply walk up to us and enter... they must be welcomed, and our flesh is their tool to get the job done. If they can tempt us to sin, and our flesh opens the door, then they will have 'permission' to access our souls and/or bodies. This is why you cannot effectively minister to a person who is not ready to let go of their bondage. If somebody is not willing to give up lust, then even if you do get them delivered (by casting out all spirits of lust, addiction, etc.), that person will likely (without even knowing it) re-open that door all over again and the demons can come right back.
Sin is a work of the flesh
Is it possible for a demon to take complete control over a person, and cause them to murder, rape, etc.? Yes! But in most situations, that is not the case.
Unless the demon takes complete control over the person, it is the flesh that commits the sin. Take for example a person who has a spirit of lust and then commits adultery... it is their flesh that has sinned, but it was coaxed along (or pressured) by the spirit of lust (or similar spirits). Having a spirit of lust can pressure us to sin, but it cannot force us to sin. This is why the Bible still refers to various sinful acts as 'works of the flesh':
Galatians 5:19-21, "Now the works of the flesh are manifest, which are these; adultery, fornication, uncleanness, lasciviousness, Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies, Envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God."
Demons are like bad friends
So what if you have a spirit of rage, and you are driven to violence? Wouldn't at least some of it be the demon's fault if you fell into that type of sin? Having a demon is like having a bad friend who has access to your mind and can sit there and inject thoughts or feelings in your system day after day. If you hang around bad friends all the time, what happens? You begin to become like them... they will wear off on you! That is what happens when a person has a demon; the demon's ways will wear on that person's flesh and break it down... making it hard to resist temptation and sin!
Can a demon take control over a person and use their body to commit gruesome acts of murder, etc.? While it can happen, it is rarely the case. Demons are great at working the flesh up to the point of sin and putting pressure on them that can be very hard to resist. This is usually how they do their dirty work in our lives.
The flesh is the open door to the enemy, and the demons are here to ruin our lives. The two work together to carry out Satan's plan to destroy us!
The flesh must be crucified (or consider ourselves dead to sin - see Romans 6:11), and demons must be cast out. If we try to crucify the demon or cast out the flesh... we are wasting our time! It is vital that we accomplish two things when seeking deliverance:
A) Make sure that our flesh is not joining hands with the demon or giving it any permission
B) Get rid of any unclean spirits that may be working against us
It is pointless to constantly discipline the flesh yet allow the demons to remain, and it is also useless to cast out the demons, but allow the flesh to re-open the doors to them again.