Evidence for Theism
19
Conclusion
It has been my concern to show that there is a God who created and sustains us and the world we inhabit. To this end I presented nine lines of evidence from philosophy, physical cosmology, molecular biology and human mental, moral and spiritual experience. In each case the phenomenon in question was shown to be credibly probable on the hypothesis that God exists and incredibly improbable on the hypothesis that he does not. Taken together, these nine lines of evidence form a powerful cumulative case for theism. [1]
Having now established both that the concept of God is coherent and that there is good evidence for his existence I have established that theism is rationally permissible: It is not irrational to believe that there is a God. And this, in turn, gives us rational permission to discuss Christianity. For if it is not irrational to believe that there is a God, then it is not irrational to suppose that God might have revealed himself decisively in human history; and if it is not irrational to suppose that God might have revealed himself in decisively in human history, then it is not irrational to assess a religion which claims to have evidence that he has done so.
However, before moving to Christian theism it is worth seeing if the present conclusion can with justification be stated more strongly; that is, whether on the nine lines of evidence just given theism is rationally obligatory. A proposition is rationally obligatory if it is irrational not to affirm it. And I suggest that in view of the nine previous arguments atheism and agnosticism both entail absurdities that it would be irrational to knowingly affirm.
Let us begin with atheism.
Recall first that to avoid the conclusion of the Modal Argument an atheist must deny the Principle of Sufficient Reason: He must hold to the principle that a physical object can exist without a sufficient reason for its existence. Schopenhauer aptly dubbed this a commission of, "the taxicab fallacy." The reason is as follows: Ordinarily, the atheist agrees that things have sufficient causes and explanations: headaches, global warming, diamonds, teapots, lightning. Indeed, the Principle of Sufficient Reason is a lynchpin of rational thought for theist and atheist alike. But when the atheist is asked to follow the principle through to its ultimate logical consequence (i.e., the universe) he attempts to dismiss it like a hired hack—and not because it is rational to do so but because he doesn’t like where it is taking him.
As we move through the rest of the arguments the cost of atheism continues to rise. Faced with the Kalam Argument, an atheist must deny the precept of Parmenides that ex nihilo nihil fit; in other words, he must believe that physical objects can pop into existence uncaused out of metaphysical nothingness. To avoid the theistic implications of cosmological fine tuning, he must (in an extravagant defiance of the principle of parsimony) postulate the existence of infinitely many unobservable universes. To explain the origin of life, he must believe that it self-assembled by chance in the prebiotic soup of the early Earth when on every reasonable calculation this is prohibitively improbable. To reconcile his atheism with the essential properties of human mental states, he must deny those properties—including free will and, with it, the rational content of his own denial. He must, finally, deny moral objectivity since morality, on his metaphysic, arises from evolutionary processes in the service of reproductive fitness. This has the absurd and unpalatable consequence that to first principles of moral reasoning (say, It is always wrong to bayonet babies for sport) he cannot give his unqualified assent. And when it is pointed out to him that his belief that, "Beliefs that arise from evolutionary processes serve reproductive fitness and cannot be trusted," is itself a belief that arose from evolutionary processes and so, ex hypothesi, cannot be trusted, he has no reply.
The entailments of atheism are counterexperiential and absurd. Atheism cannot be rationally affirmed.
On the face of it agnosticism would seem to be a very reasonable position to take. What could be more prudent than suspending judgement in matters about which absolute certainty is impossible? Note, however, that to be agnostic is to hold that, possibly, atheism is true. And since to affirm atheism is to affirm that all its entailments obtain, to hold to agnosticism is to affirm that, possibly, all the entailments of atheism obtain: It is possible that physical objects can exist without a sufficient reason for their existence; it is possible that physical objects can pop into existence out of nothingness uncaused—and so on. Clearly: If it is absurd to believe that married bachelors actually exist then it is just as absurd to believe that married bachelors possibly exist. Atheism and agnosticism cannot therefore be rationally affirmed and so it follows that theism is rationally obligatory.
However, this stronger conclusion is not essential to the argument. So long as you are willing to grant that theism is rationally permissible we are in a position to proceed to Part III: The Coherence of Christian Theism.
[1] Ten lines of evidence if we include The Modal Ontological Argument.