"Can demons return to the person whom they left? Yes, but this is mostly a concern for non-believers who have undergone a deliverance, and haven't accepted Jesus yet. Jesus warns the 'wicked generation' (sinners) that the demon can return with 7 even worse demons. If you are a believer though, and your deliverance has been complete (all the demons kicked out and legal rights have been broken), then this isn't a concern to you. However, if you go back and re-open the door(s) that let the demon in, you are re-welcoming him back in. But if we don't go back and re-punch that hole in our hedge again, we don't have have to go around worrying about it returning."

***Would agree here

"Who are we supposed to cast demons out of? Although it is possible and sometimes beneficial to cast demons out of unbelievers, the deliverance ministry is geared towards believers for a number of reasons. For one, it's part of the new covenant, which does not apply to unbelievers. Second, without Christ, you cannot remove the legal grounds the demon has in a person, therefore the problem hasn't been solved, it's only been stirred up. Third, Jesus warned that if you cast demons out of an unbeliever (sinner, wicked generation), it will come back with 7 more even worse demons and the man will be far worse then before (Matthew 12:43-45). I believe there are times when it is helpful to cast demons out of unbelievers, but that's not the focus of this ministry, Jesus said that this is children's bread (Matthew 15:26) and it is geared towards setting the believers free from demonic bondage."

***If something is not put into the void of "now no demons" then yes the demons can return.  So it is of little use if a demon/s are cast out and the individual is not brought to see the void must be filled up with the things of God. So yes the main purpose of say having the gift to cast out demons, is to bring the individual to now fill up on things of God. Maybe in the case of little children the one with the gift of casting out the demon/s would also have to power to say, "And do not return." Children can then learn to move towards God's word and way of life.

"How can a demon dwell within a believer who has the Holy Spirit? Many believe that anybody who has the Holy Spirit is immune from demonic bondage. This theology usually stems from a faulty belief that the soul (mind) and the spirit are the same things. The moment we are born again, our spirits are reborn and the Holy Spirit is united with our spirit. The soul (mind) of a man is not instantly reborn as the spirit is, but rather we are told to be transformed by the renewing of our minds, which doesn't happen instantly. Our souls is where the dirt lies, and where the demons dwell, not our spirits. Therefore, there is no reason left to believe that a Christian is immune from demonic bondage, because their souls are usually on the dirty side until they are renewed over time. 

***Really  bad  theology  here.  The  human  individual,  is  made  up  of  the  physical  body  as  a  whole;  the  blood  that  gives [with air and food and drink]  life  to  the  physical  body;  the  human  brain;  and  "the spirit in man"  which  is  from  God  and  united  with  our  brain,  to  give  us  unique  living,  different  from  any  animal.

The  subject  of  being  "born again"  is  obviously  not  understood  correctly  by  the  writer.  On  conversion  the  Spirit  of  God  unites  with  "the spirit in man"  and  the  person  becomes  a  child  of  God,  but  human  nature  is  not  destroyed,  the  pulls  of  the  flesh  can  still  pull.

If the soul and the spirit were the same things, you would instantly be a perfect person, never to sin again, once you are born again. 

***Bad  theology.  The soul is life in the blood; the "spirit in man" is separate,  and  works  with  the  brain.  You  do  not  become  perfect  and  never  able  to  sin  again  when  converted  [author  calls  it  "born again" - a Protestant fundamentalist  phrase  not  understood  by  them];  on  God's Spirit uniting with our "spirit in man" and the brain,  we  become  converted,  but  can  still  sin;  human  nature  and  Satan/demons  do  not  become  extinct,  at  our  conversion,  hence  we  can  still  sin  under  temptations.

There would be no 'evil' left in you, no desires to do wrong, and you would hate it bitterly because you would be perfect in your mind/soul and united with God, therefore there would be no room to sin. 

***Again, mixing up the wrong ideas on body, soul, spirit.  All  fully  explained  in  detail  on  my  website  under  "Death...then What?"  and  other  related  studies.  You  will  never  be  perfect  until  the  resurrection  day  at  Christ's  coming.  Until  then,  even  with  the  Spirit  of  God  united  with  the  "spirit  in  man"  you  can  still  sin.  See  1 John 1 and  into  chapter 2.

In John 8:31-34, Jesus tells us that even though they were believers, they were held slaves to sin because they were ignorant of the truth; 

***Technically  the  Jews  Jesus  was  speaking  to,  just  had  a  form  of  "belief"  in  Him,  as  He  spoke  a  few  sentences  later,  they  were  still  wanting  to  kill  Him.  Context  reading  is  so  often  ignored  and  so  leads  to  many  false  ideas.

this proves that Christians can be in bondage to darkness. 

***Other Bible NT verses show indeed a Christian can sin [Rom. 7 for starters] -  they  can  come  under  darkness  and  sin,  back  to  1 John  1  and  2.  again.

If a demon can affect our minds (souls), 

*** The "soul"  is  not  the  mind  per  se..... wrong  theology.

they can do an awfully lot of damage. Look at what mental illness can do to people through affecting the mind! 

***Mental  illness  should  not  be  automatically  associated  with  demons.  Parts  of  the  brain  can  often  "miss-fire"  -  not  run  in  a  smooth  connected  manner,  and  so  produce  mental  sickness.

They can cause the person to have unspeakable desires, thoughts, emotions, and do unthinkable things!"

***The  demons  are  still  out  there  in  the  Christian  world;  they  do  not  disappear  on  conversion.  So  yes  they  influence  you,  try  to  tempt  you  like  Satan  did  to  Jesus  in  the  40  days  wilderness  fasting  He  did.

And  as  He  said  to  Peter  once,  "Get  behind  me  Satan,  you  speak  not  the  things  of  God."  Full  demon  possession  for  a  Christian  would  mean  walking  away  from  God,  stopping  the  uniting  of  God's  Spirit  with  the  "spirit in man" - becoming UN-converted.