Proper parts and dependence

Consider this initially plausible thesis:

1. If x has a proper part, and all of x’s proper parts depend on y, then x depends on y.

Add:

2. An effect depends on its cause.

3. Nothing depends on itself.

We conclude:

4. Nothing that has proper parts is a cause of all of them.

This has a nice theological application.

5. God is the cause of everything that is not God.

6. Therefore, if God has proper parts, he is the cause of all of them.

7. So, God has no proper parts.

However, I am dubious of premise 1. I think (1) depends on a story about parthood on which a whole is made of its parts. But if we don’t have that story, we could imagine a simple thing that then goes on to produce a proper part for itself. And so we lose the nice argument for divine simplicity. Which is too bad, but there are others.