That certainly doesn't prove God exists but it definitely does make it more parsiminous. Theists are only theorising the existence of another (bigger) consciousness (one step) while adherents to the alternative theory have to imagine that there is some secret hidden substance underlying reality based on.... absolutely nothing (two steps).
In short, there is no multiplications of unknowns in theism since consciousness/mind is known to exist.
All the best,
Hypnopsi
I'm certainly sympathetic to this view (having devoted considerable energy arguing for it here and months ago (
http://www.internationalskeptics.co...?t=120937&highlight=argument+support+idealism)), but I'm not entirely sure I agree with your formulation of it.
The way you put it, the idealist is in a better position epistemically (parismoniously) because God (Overmind, as you call it) is simply consciousness to the nth degree, and we know that consciousness exists (and I would argue thought and mind as well).
However, there's still an assumption going on there- just because we have proof of consciousness doesn't mean there's a higher consciousness (God/Overmind). There's quite a big leap to go from "concsiouness exists" to "a higher consciousness exists", and we have no evidence to support the existence of God/Overmind. You bring up NDEs, and I'm also sympathetic to your view, but NDE's, even if they're not materialistically explainable, are consistent with materialistic realities (brain-in-a-vat, experience machine, being in a Matrix, etc.)
On a fundamental level, though, I agree the materialist is in a worse position. They have no proof at all for the existence of a physical substance, so their model of reality rests on basically three unproven assumptions: 1) Physical matter exists; 2) consciousness arises from physical matter and interacts with it; and 3) physical matter is either eternal or had a first cause (cause in and of itself).
The idealist has basically the same three assumptions, but for (1), the idealist has some actual evidence (the existence of consciousness). This isn't proof for (1), but it
is evidence that the building block of idealism actually exists.
On the 2nd point, the idealist is also in a slightly better position. The materialist has no explanation how or why consciousess should arise from a bunch of physical stuff (neurons), while the idealist has some evidence of the interaction of perception, thought, and mind. We all know what it is to perceive something, think about it, and experience those thoughts in our mind. For the idealist, the story gets a little fuzzy on where all the objects we experience come from (group mind, God's mind, one mind), but that is also an objection for the materalist: where did all this physical matter come from? Which leads to the 3rd point:
On the 3rd point, the idealist also has to tell a story of where the idealist stuff came from (Is it eternal? First cause?). I think it makes more sense to imagine that God has the quality "eternal" or "first cause" than a bunch of physical matter. There's nothing in physicalism/materialism to suggets that matter is either eternal or a cause in and of itself.
So it's not that there are "no multiplications of unknowns" with theism or idealism (God still remains the big unknown), but the assumptions contained in either one have a bit more evidence to support them, and on the question "Where did it all come from?" The idealist (and/or theist) has a more convincing story.