It is possible to understand the idea of idolatry in a Kantian sense.  I might try to give some background about what I mean but the basic idea is simple. God is one, not two or three and he is not a composite. According to the Torah he is not the world nor is the world him. He is the First Cause that caused everything that exist to exist. That is to say he is transcendent and one and ideas of form and substance do not apply  to him.
With Schopenhauer we get further that he is the only unconditioned reality, though that is not like Kant.
What you get from this is a kind of clarity about God but also you get the idea of a limit how far human understanding can go about him. That is the apt title of the Critique of Pure Reason.

This helps to understand the idea of idolatry--which I found very difficult to understand. The major help I found about idolatry was reading the book of Daniel and later learning pages 62b in Sanhedrin and on-ward. [ie 62b -circa 64]. Of course the Nefesh HaChaim was helpful to some degree in the place where he deals with the problem of worship of people.[That is the chapter where he explains the idea of service of God as intending to get attached to God through prayer (I think.) I don't have t to be able to look it up.]


So in short unconditioned reality is unconditioned reality and thus idolatry is simply trying to make it concrete.