Philosophy may invalidate others’ reasoning due to logical fallacies, but it is impotent in establishing positive truth.
Voegelin's philosophy starts with an article of faith and therefore can only produce new articles of faith.
IMHO any philosophy that claims to establish positive truth is not philosophy, but something else masquerading in the costume of philosophy. And certain schools do assert this (e.g., positivism, phenomenalism, materialism; utilitarianism, etc., all post-Enlightenment "diremptions" from the classical philosophy). I'm just confirming your observation here PasorBob.
But this does not mean that there is no truth in philosophy. Philosophy explores aspects of reality that are not "physical," or "material." If I wanted to understand the relations between mind and world, for example, would science be of any help to me? Science doesn't have much to say about mind, or psyche, or spirit; and if it has a concept of "world," or even of "reality," it didn't get it from the exercise of the scientific method, but from philosophy.
So clearly philosophy must be a means of acquiring knowledge; for otherwise, how could worldviews arise in the first place?
Please tell me what Eric Vöegelin's "article of faith" is? I've been a student of his for a while now and am most curious to know your view of this.