These are not my thoughts. They merely occurred to me.
It is the knowledge you hold of God. Your idol summarizes that knowledge. You become a slave to a fake God made out of your knowledge, created by you.
Therefore, those who know God absolutely don’t know it. They merely think that they do. This pride keeps them imprisoned. It doesn’t allow them to step into the realm of the unknown.
Update on Sep 23 -
I removed the last paragraph because it was confusing people. Also, I took a spin on idolatry here if anyone's interested.
Update on Oct 18 -
When you worship an idol, you give the formless a form, which blinds you from all other forms it can take. Perhaps, all forms are manifestations of the formless. Take love for example. Love takes different forms in dogs, cats, cows, birds, trees, and humans. Even among humans, it takes different forms in men, women, and children. When you hold only one of its forms to be true, you become blind to every other form it can take.
In addition, so long you worship an idol, you are a slave to the makers of the idol. I have explored this idea here.