Here are four combinatorially possible ways truth and God could be related.
1. There is truth, but there is no God.
2. There is truth, and there is God, but God is not the ontological ground of truth.
3. There is truth, there is God, and truth ultimately depends on the existence of God.
4. There is no truth, and there is no God.
(4) is suggested by Nietzsche's perspectivism in tandem with his notion that the death of God brings in its train the death of truth. (4) is easily refuted. I will say no more about it in this entry. The other three (epistemic) possibilities are live options. My atheist friend Peter Lupu, at a conference at Glendale CC yesterday, espoused (1). He thinks, as I do, and as any intelligent person must, that truth is objective and absolute. We also agree on what we mean by 'God': roughly, the omniqualified supreme personal being of the Abrahamic religions.
Peter and I also agree that, in one sense of 'there is truth,' it means that there are truths, where a truth is a true truth-bearer. For Peter, and this is surely very plausible, truth-bearers are Fregean propositions. So for Peter there is a realm of objective truths, and one of the truths in this realm is that God does not exist. It obviously follows that for Peter what truth is, whether it is, and which truths there are, have nothing to do with God, with the sole exception of the truth that God does not exist and whatever it entails. There is a realm of Wahrheiten an sich, and they subsist in splendid Platonic independence of minds, their contents, and other concreta. Obviously, if there is no God, then he can play no role with respect to the existence of truth, the nature of truth, or which truths there are apart from the truth that he doesn't exist and its entailments.
As for (2), consider a theist who agrees with most of the foregoing but affirms that God exists. Then the dispute between this theist and Peter boils down to the question whether the Fregean proposition *God exists* -- which both admit exists in Frege's Third Reich (realm)-- is true or false. For a theist of this stripe, the existence of God has no bearing on whether truths exist or what the nature of truth is, but it does have a bearing on which truths there are. For example, given that God exists, then *God exists* is true, and if God creates a physical universe, then the truth of *A physical universe exists* depends on God and his free decisions.
I incline to position (3). The position I would defend is that if, per impossibile, God did not exist, then truth would not exist either. Why do I say per impossibile?
God has the Anselmian property: if he exists in one possible world, then he exists in all. Contrapositively, if God does not exist in all worlds, then he exists in no world and is thus impossible. So if God exists, then he exists necessarily. It is also easy to show that if some truths exist, then necessarily some truths exist. But despite the broadly logical equivalence of the existence of God and the existence of truths, despite the fact that in every possible world in which the one exists the other does too, and vice versa, there is an asymmetrical dependence relation of ontological grounding: the existence of truths depends on the existence of God, but not vice versa.
The theist above is committed to
A. Necessarily, truths exist if and only if God exists.
I affirm (A) but take it a step further:
B. Necessarily, truths exist because God exists.
The 'because' in (B) is not the causal 'because'; it expresses the asymmetrical relation of ontological (metaphysical) grounding. Anyone who balks at that relation does not understand what metaphysics is. (Some defense of the relation here.)
Peter must reject both of (A) and (B).
Now what reason might one have to think that (B) is true? Different arguments can be given. Here is one by Anderson and Welty together with my additions and criticism. The gist of the argument is as follows. There are necessary truths, among them, the laws of logic. A truth is a true proposition, a proposition that has the property of being true. But nothing can have a property without existing, and nothing can have a property (in this instance, being-true) necessarily unless the thing in question exists necessarily. Now propositions are intrinsically intentional. But only thoughts are intrinsically intentional. So propositions are thoughts. (Here is where one can reasonably object.) Necessarily true propositions are necessarily true and necessarily existent thoughts. Thoughts, however, are necessarily thoughts of a thinker (subjective genitive). No thinker, no thoughts. The thinker of necessarily existent thoughts must be a necessarily existent thinker. "And this all men call God." This is but a sloppy sketch; bang on the above link for a more rigorous treatment.
In my critical comments on the Anderson-Welty argument, I claim that the argument is rationally acceptable, but not rationally compelling. But then no argument for any substantive metaphysical thesis is rationally compelling. And this extends to all the arguments of atheists.
Where does this leave us? The discussion will continue through a ramifying series of arguments and counterarguments, but I won't be able rationally to compel Peter to abandon his atheism, nor will he be able rationally to compel me to abandon my theism. There will be no progress toward the ultimate resolution of the question, but there will be progress in the elaboration and clarification of our respective positions.
In the end one must decide what one will believe and how one will live. And we must tolerate those with opposing views -- but only if they requite tolerance with tolerance.