Arguments about nature, gods, and human beliefs are often convoluted and massive. The central issue can be boiled down to a manageable residue.
The phrases “mental substance” and “independent identity” are incoherent. They are combinations of words which indicate nothing but the byproducts of speech. At best, their proposed subjects are things which we could not claim to know. That is why all arguments in their favor must finally deduce from analogy, if they hope to avoid fideism. All else follows.