OK, this may be simplifying things too much, but it is the easiest way I could communicate this. I believe that we are all given a choice as to whether we want to follow Jesus or not. When we make a choice, we then end up either 'for' God or 'against' God. To take the illustration further, we are either part of God's side or not.
This is not a fickle judgement, but rather a result of a decision we make. Just like, in a battle, we can't fight for the same side - we are either supporters of one side or of the other side. Take your favourite sports team as an example - when you play another team, you support your team through thick and thin - it's a choice we make.
However, many people often choose to live in spiritual "No Man's Land", which has been described as follows:
"No man's land is land that is unoccupied or is under dispute between parties that leave it unoccupied due to fear or uncertainty."
This may be OK for a while, but this is also dangerous territory. I am not sure that the devil sees 'no man's land' as neutral ground - I think he sees it as a great chance to get some more supporters.
"Be alert and of sober mind. Your enemy the devil prowls around like a roaring lion looking for someone to devour." - 1 Peter 5:8
These are just my thoughts - what do you think?
Living in Grace