This post was inspired by the writings of Paul Draper. If you like the argument, the credit should go to Draper. Any problems with the formulation below, however, are probably due to an error on my part.
Informal Statement of the Argument
Humans are effectively self-centered; our tendency to behave in self-centered ways is usually much stronger than any tendency to behave in selfless ways. These selfless or altruistic behaviors can be divided into two types: kin altruismand non-kin altruism.
On Darwinian naturalism, the mixture of moral goodness and moral badness we find in Homo sapiens is easy to explain. The Darwinian naturalist explanation for our overwhelming tendency towards self-centered behavior is obvious. Kin altruism is also easy to explain: behaviors that promote the survival and reproduction of my kin make it more probable that my genes will be inherited by future generations. Non-kin altruism is weaker than kin altruism and also absent more often than kin altruism. Given that kin altruism exists, this pattern or distribution is exactly what we would expect on Darwinian naturalism.
On theism, either God created humans directly (special creation) or indirectly (Darwinian theism or theistic evolution). Since God is omnipotent and omniscient, He could create humans without making them inherently self-centered. Since God is morally perfect, He would have good moral reasons for creating altruistic humans. Furthermore, He would not create inherently self-centered humans unless He had a morally sufficient reason for doing so. So given that humans are inherently self-centered, theism entails both that God is not constrained by biological goals like survival and reproduction (and hence does not need to create human beings who are inherently self-centered) and that He had a morally sufficient reason for doing so. And that’s a really big coincidence that Darwinian naturalism doesn’t need.
Formal Statement of the Argument
B: The Relevant Background Information
1. Living things, including sentient beings, exist.
2. The biological goals of goal-directed organic systems include survival and reproduction.
E: The Evidence to be Explained
Let E be observations of the self-centeredness and limited altruism of human beings. E can be broken down into three specific observations:
E1: Humans are basically self-centered.
E2: Kin altruism
E3: Social altruism is weaker in most humans that kin altruism. It also frequently absent altogether. Social altruism is also usually much more limited in scope.
Hypotheses (Core and Auxiliary Hypotheses)
Core, rival hypotheses:
T: classical theism
N: metaphysical naturalism
D: Darwinism: the theory that natural selection operating (indirectly) on random genetic mutation is the principal mechanism driving the evolutionary change that results in increased complexity
The Argument Formulated
Let “>!” mean “is much greater than”
(1) Pr(E | B & D & N) >! Pr(E | B & D & T).
(2) E is known to be true.
(3) T is not much more probably intrinsically than N.
(4) Therefore, other evidence held equal, T is probably false.