I don't think its really about a lack of faith...they were trying to cast out the demon already
Many people in the west deny the reality of the spiritual realm and either fear or exaggerate demonic activity.
If Jesus said 'this kind' , meaning the demon (s) , He was referring to the fact there are different kinds of demons
Jesus had all authority over demons..we have authority over them IN Christ....in fact, Jesus said Christians would cast them out
Its not a power struggle...its a truth affirmation. ..Jesus is Lord!
Mark 9:17-24
King James Version(KJV)
17.)And one of the multitude answered and said, Master, I have brought unto thee my son, which hath a dumb spirit;
18.)And wheresoever he taketh him, he teareth him: and he foameth, and gnasheth with his teeth, and pineth away:
and I spake to thy disciples that they should cast him out; and they could not.
19.)
He answereth him, and saith, O faithless generation, how long shall I be with you? how long shall I suffer you? bring him unto me.
20.)And they brought him unto him: and when he saw him, straightway the spirit tare him; and he fell on the ground, and wallowed foamin.
21.)And he asked his father, How long is it ago since this came unto him? And he said, Of a child.
22.)And ofttimes it hath cast him into the fire, and into the waters, to destroy him: but if thou canst do any thing, have compassion on us, and help us.
23.)Jesus said unto him,
If thou canst believe,
all things are possible to him that believeth.
24.)And straightway the father of the child cried out, and said with tears, Lord, I believe; help thou mine unbelief.
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When you voted "other" were you talking about verse 24?