Morality itself provides a rational warrant for bleief in God.
(1) The normative nature of Moral Axioms is universally Recognized.
(2) Explanations must account for the universal imperative while preserving the normative aspect.
(3) Materialist explanations cannot preserve the normative aspect because they lack a basis for moral moral judgement (they can't supply a justification for the "ought").
(4) The concept of God provides the basis for Moral Judgement since God is omniscient, just, and compassionate.
(5) Therefore,since the concept of God provides the best explaination for the normative nature of moral axioms, and since we asssume the reality of the we we have a warrant for beief in God as a regulartoy concept.
Even though the mores may vary, all civilizations and cultures have a strong sense of moral outrage at gross injustice and a sense of fairness and desire for the right to win out. This seems like an innate sense. The real trick is not explaining how this innate sense came to be but explaining it in such a way that we can still take it seriously as a normative value.
Materialistic and naturalistic explanations can easily explain how the need for the moral dimension arose from naturalistic sources but they cannot explain why we should take it seriously as moral.
The Apostle Paul tells us that there is a universal moral law written upon the human heart (Rm 2:6-14). We can see evidence of this universal law throughout the world. Now social science is quick to tell us that moral codes of all cultures differ throughout the world; some are so drastically different as to allow for multiple mirages, in some cultures gambling and even cheating each other are expected, and in a few cultures there doesn't seem to be any notion of right and wrong. But we shouldn't expect that all the moral codes of the world would be uniform just because there is a moral law. The evidence of a universal law is not seen in structured belief systems but in the humanity of humans. People in all cultures have concepts of right and wrong, even though they may attach different kinds of significance to them. There are a few cultures that are actually pathological examples, but in the main most people are capable of being good, exhibit a basic human compassion, and feel moral outrage at cruelty and injustice.
It is this sense of moral outrage and the ability to empathize and to feel compassion that marks the moral law best of all. In Nicaragua in the 1980s members of the contra army fighting the Sandinistas conducted a campaign of terror to prevent the people from supporting the revolutionary government. To enforce a sense of Terror they cut off the heads of little girls and put them on polls for all to see  The modern equivalent is Issis. People are also repulsed by their doings. There is something about this act, regardless of our political affiliations which fills us with anger and revulsion; we want to say it is evil. Even those who believe that we must move beyond good and evil are hard pressed not to admit this sense of outrage and revulsion, yet if they had their way we would not be able to express anything more than a matter of taste about this incident for nothing is truly evil if there is no universal moral law.
(1) Genetic explanations only provide an understanding of behavior, they do not offer the basis of a moral dimension (trying to turn "is" into "ought").
(2) Social contract theory offers only relativism that can be changed or ignored in the shifting sands of social necessity and politics (this is both a practical issue and a matter of meta ethical theory).
(3) matters of feeling are merely matters of taste and should be ignored as subjective (the atheist dread of the subjective).
(4) God is possessed of a loving nature that makes the good a matter of rational on the part of the creator and his status as creator means he is more than qualified to be judge to translate te good into moral values.
 Noam Chomsky, Turning the Tide:U.S. Intervention in Central America, South End Press; First Edition edition (July 1, 1999)