Logic and Medieval Theology

Like any logical structure, a sound theory includes premises which are self-evidently true.  Now, the premises of Medieval Theology, typically--1. God exists, and 2. God is one, transcendent, incorporeal, good, and omnipotent--may be true, but that they are self-evidently so is questionable.  For example, the standard grounds for their acceptance--that they are products of an interpretation of Biblical texts, that they are objects of faith--are hardly self-supporting.  So, the originality of Descartes and of Spinoza can be appreciated as logical critiques of Medieval theory--the former replaces both of its premises with 'I think', while the latter jettisons #2, in favor of 'God and Nature are identical'.