Apologists often posit that the ultimate explanation for reality, or the existence of the universe is some type of God. This, to them, is an accounting for things such as morality, knowledge, and aesthetics. An accounting here is some type of metaphysical explanation for things like what is ethical? Or what is knowledge? Or what is the truth? For example, in science we observe a natural phenomenon and we attempt to make a model with both explanatory power and predictive capabilities. Given that I observe a ball being thrown by someone S₁ (causal or efficient agent) to someone S₂, and I am then asked the question: Who threw the ball? The obvious simple explanation would be the person who threw the ball, in this case S₁. But merely knowing who threw the ball isn’t an actual metaphysical explanation, nor a metaphysical account.
If however the question is: “How did the ball get thrown from S₁ to S₂?”, then it asks for more of a scientific accounting which can be explained by kinematic theory (kinematics). Which in turn is explained more basally by the general theory of gravity. The theory of gravity not only explains the parabolic like trajectory of the ball from S₁ to S₂, but also can make a prediction that given the exact same initial conditions, that ceteris paribus, we can predict that every time that the ball will move in the same exact path from S₁ to S₂.
A metaphysical accounting can be explained by various modeling and metaphysical theories such as various theories of truth (Correspondence, Coherentist, deflationary theories, semantic theories, pragmatic theories), or of knowledge (Justified True Belief, JTB+, semantic theories, pragmatic theories), or of justification (coherentism, foundationalism, foundherentism, infinitism, reformed epistemology, evidentialism, reliabilism). For example, let’s say we want to have accounting of beliefs and how they actually correspond with reality or specifically this actualized world. To a theist positing a God, they can claim that a particular belief God exists is warranted by an externalist view of reformed epistemology (Plantinga), which has elements of foundationalism, in that they posit God to be properly basic and rational regardless or independently of evidence, and of epistemological reliabilism as it is based upon proper cognitive functions.
If a theist, however, posits a God as more of the ultimate explanation for everything (Why there is something rather than nothing? How did the universe come into existence? Why do we hold value in things?) they are putting God as the foundation for the grand unified theory of everything. This to me seems metaphysical tenable only as far as some type of epistemic justification of beliefs as to why a theist justifies their belief that God exists…it however fails as a holistic explanation for everything on two accounts.
First, positing an agent as an explanation is merely a simple explanation of causation. If we again ask who threw the ball, we can respond that the agent (the efficient cause) S threw the ball and the question is sufficiently answered. This however lacks any type of predictive ability, since if S threw the ball again to S’, we can not predict it will take the same type of path because we don’t have sufficient information to make such a prediction…thus the accounting is incomplete. If instead, however, we ask “Can we explain and predict under specific conditions if S throws a ball to S’, the path the ball will take?”…then the accounting would of course be the general theory of gravity or kinematic theory; both of which would have explanatory power to explain, and make accurate predictions. So saying “Goddidit” would only be a simple explanation of if we asked a question, presupposing an agent was the cause of something that has taken place. God here would merely be analogous to person S₁ if an agent to explain an observation, and as such just as much as an incompletely accounting.
Second, positing God is ad hoc for any type of complete metaphysical accounting. It is merely something posited as necessary, but merely because at this time we just are not able to fully account for reality…and perhaps no accounting for reality is even possible. This is often referred to as to as “God of the gaps”. Unless we knew the means by which God created reality, by maybe asking him questions about reality, and then could model it…that perhaps would be be a sufficient accounting for “everything”. It would be analogous to the question “How did The Great Pyramid of Giza get built?”. If we answered, the Egyptians built it…does that sufficient answer the question? While it is a simple or nominal explanation, it lacks any real explanatory power or predictive ability. Even if some more exotic explanation was the case, such as as “aliensdidit” that would also be ad hoc lacking any explanatory power or predictability and fails as any type of account of how the Great Pyramid was built. However, if we did discover aliens built them, and then were able to ask them how they did it so we could make a repeatable model using their technology…then that would be a far more sufficient accounting of how the Great Pyramid was built. Even though, it would be insufficient as a metaphysical accounting for the same reasons we do not yet have a metaphysical accounting of reality, merely scientific theories to account for what we observe (Big Bang, General theory of gravity, special theory of relativity).
So can God account for anything? Well if God exists, we would be only able to answer that question if we could somehow make a model or theory of how God created reality. So even if we knew God exists, it still would not be sufficient to explain anything…and I think that is were most apologists who posit God as the ultimate explanation fail.