phoenix: it makes me wonder if a theory of everything will have to incorperate the tools of science and theology.
in the reply, there was a mention of physics.
when i say everything, i mean everything whereas when someone else says everything they might just mean the four known forces.
so what i said amounts to saying that a theory of everything might require tools of science and theology among other tools.
someone asked what might go on the other side of an equation like God= ? some people would say that God=all that is.
i'm not sure how to evaluate a statements that have appeared here in the form X is a subset of Y when the word spirituality is involved. words like spirit and spirituality have different definitions.
i have heard of three "paths to God": mind, heart, and action. i suppose you could call spirituality the study of those paths but for some people, spirituality has nothing to do with God.
i don't think we'll ever be able to give a proof of God's existence with logic, starting with a definition of God, or observation/empirical data.
some people think that God is all that is. the author that thinks God is all that is also defines knowledge to mean that A knows B if A=B. the "argument" is that i can know about a cat but to know a cat i have to be a cat. if God is all that is, then it's clear that God is omnipresent. also, being all that is, with this definition of knowingness, God knows everything and is omniscient. i don't see how omnipotence follows from this definition...
other people may start with an assumption about God being omnipresent which would entail, at least, that God is within all that is. but then, if there were something in "all that is" that God isn't a part of, God wouldn't be omnipresent; so God is all that is.
if God is all that is, then God exists if and only if "all that is" exists. in other words, if at least one thing exists, then God exists. however, if nothing exists, then, of course, God doesn't exist. it was an "if and only if" statement.
i don't think one will ever prove the existence of God from definition alone. something else is required, perhaps observation though people don't always take observation to constitute absolute proof due to it's possible (or assured) subjectivity. for example, the following statement is considered by the rules of logic to be "true": if x is an element of the empty set then x is a purple goat controlling my thoughts. in some sense, you might call vacuous truth kinda weak, but it's basically saying that if x doesn't exist then you can say anything you like about x. what I'm trying to say is that arguments based on definitions of God and logic alone don't prove God exists. i could construct a mathematical example where i define something and even discuss its properties but that doesn't even prove it mathematically exists, which is probably easier than proving that it really exists (unless you consider mathematical existence to imply existence).
all I've done above is say that if God is all that is then God exists if and only if all that is exists.
if you accept that God is all that is and if you accept that at least one thing exists, well then it follows that God exists. if you don't accept that definition of God, it doesn't automatically follow that God doesn't exist.
let's take this in a different direction and consider a proof not based on definition and logic but observation. let's not even consider God, let's just say i claim to be either immortal or omnipotent. i don't think i can ever prove that i am either immortal or omnipotent, though i might convince you that i am even if all the evidence i give you is circumstantial. let's just take immortality. how can i prove to you that i am immortal? think about it. i can't. the only thing i can do for you is disprove the claim by dying. however, i may outlive you. that just means i outlived you, it doesn't mean i'll live forever. suppose i live for a googleplex years. that still doesn't prove i will always live. (however, i have heard that some scientists think a claim is true if it is consistent with reality so far. if that is the case, it's already true that i am immortal because that is something that is consistent with reality so far. the flaw with this conception is that even time-independent claims may be true one day and not true the next.) you can do something similar with omnipotence. i may be able to lift a billion tons of rock but then you can always ask if i can lift 1,000,000,001 tons. nothing i can do will prove i am omnipotent. although thinking about it a bit more reveals that if i am omnipotent, i have the power to prove it to you.
let's just say that i can prove i am omnipotent, omnipresent, omniscient, perfect, the first cause, and all that jazz (which i think is highly unlikely though i may be able to convince you of it). then how would i prove that i am the christian God or G-d or Allah or The Great Spirit or blah blah blah? (hope you can excuse the reference to religion.)
thus, both logic and observation will not prove God exists.
what would?
well, if you were omniscient, you would be able to know if i were God. too bad we're not omniscient...
i personally think the statement "God exists" is undecidable but i can't prove that it is.
however, at least in certain situations, there are statements which are on some level true though they cannot be proven to be true in finite time. so, and this is just my opinion, "God exists" is a true statement but there is not nor will there ever be universally acceptable proof. that is unless God makes us all omniscient. then we would by definition know if there was a God.
) that integrates all of the four natural forces can be arrived at without taking into account whether or not such a creator exists. 
