(Taken from a crude thought experiment I conducted with help from Keith Neilson of NBCC in 2009.)
The matter of God is an oft-argued point, and the primary problem with such discussions is that nothing can be proved or disproved in absolute and scientific terms. This was because Science was not developed to theorize on matters of supernatural concern, but simply on natural problems. God (or any Deity) is a non-quantifiable entity, existing outside of the normal framework of nature. Under many (if not all) belief systems, a deity is an omnipotent or suprapotent entity. Omnipotence implies a supernatural nature, as omnipotence implies the ability to ignore and even alter natural laws. Therefore is God outside the scope of science.
An argument can be made, however, on the basis of analogy. Consciousness (id est sentience) is also unmeasurable. With the exception of agreeing upon the nature of given qualia (two men agreeing that red is in fact red, and green is in fact green), two separate consciousnesses cannot communicate their exact methods of perception. This has been called the Color Problem, where, in layman terms, though you and I will both agree on what is yellow, the colour I see "for" yellow could be the one that your mind uses to register the qualia of, say, red. Therefore, two consciousnesses cannot truly know each other, and are unmeasurable. Barring some new development, consciousness is also outside the scope of science, but we know that it exists, because we know that we are conscious. This consciousness is not the state of wakefullness, but the total package that separates one mind from another; personality, memories, inferences, and biases, what some might loosely refer to as a soul.
A curious consequence of the mechanism of consciousness, which is activity of the brain, is that the mechanism by which consciousness functions can be detected (even if nothing truly insightful can be so inferred), in the form of chemical reactions and their related electrical activity. Consciousness has an associated energy; the electrical activity of the brain.
Can a similarly-measurable Energy be associated to a Deity? Consider the following question.
Given the currently theoretically sound cosmological model, and the laws of Thermodynamics, where did the initial impetus that began the universal expansion (an event known as the Big Bang) originate?
Consider: Matter and Energy cannot be created or destroyed, merely converted from one form to another. We know of a link between matter and energy thanks to Einstein's famous equation, E=mc^2. It is possible to convert energy into matter, and vice versa.
For the universe to have begun expansion, the matter/energy would already have needed to be in place. It therefore becomes necessary to assume that some extra-temporal source of either existed as time also began with the Big Bang in the current model. A large reservoir of energy, the sum total of all the energy of the universe.
The reality perceived by a consciousness is subject to its mechanics; few argue that there are objective qualia in the universe upon which all humankind can agree without any need for education, and the agreeable qualities of the world grow with further experience and education thereof. However, we also know that this reality is still shaped by the function of the consciousness. Various mental illnesses (particularly the schizophrenic disorders and other related problems) can alter, sometimes dramatically, the composition of the universe as experienced by that particular individual, and this is often reflected in a change of the energy and activity of the brain, or by damage to its tissues. Similarly, can't we argue that the mechanisms and reality of the universe are determined by the matter and energy that comprise it? It is evident.
Interactions of matter and energy in the universe are governed by a series of constants, which define various fundamental forces. Changes in these constants has been demonstrated through mathematical simulation to have wide-reaching consequences for the universe in which the change has differed. However, many of these constants are unknown, or imprecisely known (i.e., are numbers with uncertain digits). These constants could be argued to be the mental state of a Deity. Because the nature of the universe is consistent and constant, we can rule out the possibility that there are multiple deities, if we assume that there is a single universe. This is the only reasonable assumption to the number of universes, as this is the only number of universes which can be measured.
Therefore, a Deity exists, and existed ex temporae with respect to our Universe, which is a consequence of the analogous process of It's consciousness to our perceptual consciousness. It is therefore subject to further consideration as to its proper identity. With respect to various mind-over-matter phenomena in humankind (including the property of Free Will), it is reasonably arguable that the said Deity is capable of circumventing the natural laws of the universe by exercising free will, which would be a functional omnipotence. Such a Diety would exist as long as the universe and would be "alive" so long as energy within the universe persists, functionally immortal. Such a Diety, given infinite time and self-insight, would theoretically know the precise state of its associated universe, which is functional omniscience.
We may therefore posit the existence of an Omnipotent, Omniscient, and Immortal Diety. Further consideration as to the identity of such a deity is necessary, and is dependent on observation of the current universe. It would therefore be impossible to entirely quantify such a Deity, as, beyond qualia, the precise nature of the universe can be altered by the mental state of the individual observer. It is therefore upon the observer themselves to identify or discern their God, but it is also reasonable to assume that the vast majority of Humankind should be able to determine reasonably similar Dieties.
This thought experiment hazards no guess to the identity of our universe's Deity, or to the possibility that such a Deity has communicated or is communicating with humankind through readily understandable means.