The Moral Argument studies humanity and infers that our moral nature is evidence for a personal God. Basically, the argument states that humanity has shown remarkable consistency in its “oughts” across time and cultures. An appeal to a sense of “oughtness” suggests a Moral Law, which in turn suggests a Moral Lawgiver. Just as a knock on the door implies someone is knocking, a demand on the conscience implies a person making the demand.
C.S. Lewis’s popular explanation of the Moral Argument arrives at a Christian conclusion. He says that there must be a moral law, or moral disagreements would be senseless, moral criticisms would be meaningless, and moral obligations would be unnecessary. Since there is a Moral Law, we must posit a Moral Lawgiver who is interested in our behavior and gives us laws accordingly. Furthermore, this Lawgiver must itself be Good, or there would be no objective standard, and moral effort would be futile. Therefore, there is an absolutely good Moral Lawgiver.
Unlike Lewis, Immanuel Kant viewed God’s existence merely as a “morally necessary presupposition” rather than a proof. His famous categorical imperative states that we desire happiness, and we are required to be moral; therefore, the uniting of happiness and duty is the highest good. Since finite humans cannot achieve this perfection, and the moral necessity of something implies possible attainment, one must posit a being that has achieved this perfection.
A third form of the argument points out the degree to which people in very diverse cultures and epochs have reached an astonishing degree of agreement on moral judgments.
Modern expressions of the Moral Argument have taken a variety of forms. W.R. Sorley notes that since natural law is descriptive of the universe, while moral law is descriptive of human behavior, moral law cannot be part of the natural world; therefore, there must be a Supreme mind in which moral law exists.
One criticism of these arguments states that the idea of commanding someone to do or not do a particular deed is contrary to the very essence of ethics. From this perspective, a truly moral decision can only be made by persons under no moral obligation to any outside source. Proponents for this view argue that “laws, rules, and regulations are of the right logical type to be laid down in accordance with, or in conflict with, the moral law. But the moral law itself is not the sort of thing that needs to be, or that logically can be, laid down or promulgated by anyone.”
Kant’s argument has also been faulted for assuming there is a moral obligation to attempt to attain the highest good. In fact, one could argue that people are under no obligation to attempt to reach a goal that Kant himself admits is unattainable.
Still other critics have noted that the idea of an objective moral law no ways implies the necessity of that law, since imperfect minds can still think of perfect ideas. Trueblood responds to this type of argument by basically stating that “unless we assume the universe is irrational, there must be an objective moral law and, thereby, an objective Moral Law Giver.”
 Copan, Paul. “The Presumptuousness of Atheism.” Ravi Zacharias International Ministries. 2003. Internet. Available from www.gospelcom.net/rzim/publications/essay_arttext.php?id=3. Accessed May 23, 2003.
 John Bowker, ed. “Moral Argument for God’s Existence” The Oxford Dictionary of
World Religions. (Oxford: Oxford University Press, 1997).
 “Moral Argument.” Basictheology.com. 2003. Internet. Available from www.
Basictheology.com/main/definitions.display.asp?did+56. Accessed April 23, 2003.
 Geisler, Norman. “Moral Argument for God.” Baker Encyclopedia of Christian Apologetics. (Grand Rapids: Baker Books, 2002), 498.
 Paul Edwards, ed. “Moral Arguments for the Existence of God.” The Encyclopedia of Philosophy. Volume 5. (New York: The MacMillan Press, 1967), 382.
 Geisler “Moral Arguments,” 499.
 Edwards “Moral Arguments for the Existence of God,” 382.
 Geisler “Moral Arguments,” 499.