Since the beginning of philosophical speculation, there has been controversy over the existence of God or gods. Among the Pre-Socratics, Democritus denied all deity and affirmed a materialist philosophy of atoms in the void, and nothing more. Other early metaphysicians discerned traces of the divine in the natural world. For Heraclitus, beyond the perpetual flux lay the mysterious Logos, which provided order and a kind of moral ecosystem for the world. Anaxagorus attributed the order of nature to something immaterial, Nous (Mind). Although the Pre-Socratic philosophies were inchoate and their theologies (or a-theologies) were metaphysically minimal, we find in them the first philosophical debate over whether anything transcends the natural world.[1]

The debates have continued ever since. Atheism gained ground philosophically and culturally in the West, especially after the Enlightenment. However, atheism has been losing ground in recent decades due to the rise of academically rigorous philosophical defenses of theism and critiques of atheism from luminaries such as Alvin Plantinga, Richard Swinburne, William Alston, William Lane Craig, J. P. Moreland, and others. The publication in 2004 of Sam Harris' pugnacious and polemical The End of Faith catalyzed a brand of atheism that didn't so much refute theism at its philosophical best but rather condemned religion in toto.

The Twilight of Atheism was written by the prolific Oxford theologian Alister McGrath, just before the rise of the New Atheism. Instead of looking at the intellectual reasons that atheism might be in decline, McGrath focuses on cultural and historical forces. McGrath writes in a graceful and knowledgeable manner, but he is unphilosophical in his approach to the debates between atheism and Christianity. While we should not expect a historical theologian to glean every nuance from technical philosophical debates, McGrath fails to explain or assess any of the pertinent philosophical issues regarding the existence or nonexistence of the deity. Instead he surveys the intellectual and cultural climates that led to the rise of atheism, from the Enlightenment until its recent twilight. (The book lacks footnotes or endnotes. Instead there is a long list of "works consulted" at the end of the volume.)

McGrath claims that much of the atheism of the Enlightenment was more a rejection of corruption in the church than anything else. He argues that Enlightenment rationalism and secularism seem to be in crisis for various sociological and historical reasons; the pluralistic conditions of postmodernity are breaking down the hegemony of unbelief as the only rational approach to life. However, many readers, especially those with more than a passing interest in philosophy, will be left wondering whether these trends away from atheism and toward theism are intellectually justifiable. That is, what are the best arguments for and against God's existence both today and in Western history?

On this, The Twilight of Atheism has next to nothing to say. Indeed, McGrath injudiciously asserts that philosophical argument for and against God's existence has "ground to a halt." If he means that philosophers have reached no consensus as to the rational status of arguments for God's existence, he is surely right. But then philosophers seldom reach consensus on anything, especially the great matters of metaphysics. This is no reason to conclude that these debates are dead.

If McGrath means that new lines of inquiry on the existence of God have failed to emerge in recent decades, he is also mistaken. In a long and distinguished line of books defending natural theology, Richard Swinburne has shifted theistic arguments from deductive forms to inductive forms using sophisticated probability reasoning not previously employed in metaphysical arguments. Alvin Plantinga's modal version of the ontological argument (using the semantics of possible worlds) has breathed new life into an ancient and alluring argument first invented by Anselm and subsequently advanced by a who's who of philosophers. In the last thirty years, William Lane Craig has revived and repeatedly defended—both in popular and academic settings—an even older theistic argument, based on the impossibility of the universe having an infinite past (as I will discuss below).

By summarily affirming methodological naturalism in his chapter on the "warfare" between science and religion, McGrath also ignores the significant challenge to naturalism (and boost for theism) posed by the Intelligent Design movement, which claims that certain features of nature are explained better by intelligence than by merely material causes. While the Intelligent Design movement is more a critique of naturalism in science than a positive program of natural theology, its method of design detection contributes significantly to the design argument for God's existence. But McGrath is silent about all of this.

 Nor does The Twilight of Atheism have anything to say about the rise of the Society of Christian Philosophers and the significant impact made by Christian philosophers in the academy in the last thirty years. Yet the book offers an entire chapter recounting the dysfunctional machinations of famed atheist Madelyn Murray O'Hair and her fractious disciples—events having little to do with the intellectual issues at hand.

 When McGrath does deal with the rational assessment of natural theology, he says nothing more than that God's existence cannot be proved, since faith is required for Christian belief.[2] Having dismissed all progress in theistic arguments, McGrath claims that belief in God is determined more by the imagination than by rational argument. The role of imagination in religious belief cannot be disputed nor should it be avoided, but as Pascal warned in a memorable fragment in his Pensées, imagination can often lead us astray when untethered from knowledge. Some of the best apologetics invoke the imagination liberally (think of C. S. Lewis and G. K. Chesterton), but the imagination must illustrate and amplify what reason declares. If reason cannot decisively inform the debate between theism and atheism, then one wonders how a Christian can claim to have any knowledge (justified true belief) about the object of supreme significance (God).

The Twilight of Atheism gives a diagnosis that the patient (atheism) is failing, but offers no philosophical argument as to why the patient should be failing. It claims only that, philosophical arguments for God having petered out, we need a new infusion of religious imagination to do the job. As such, it does little to advance the great debate one way or the other.

Indeed, philosophically inclined atheists seldom take the refusal to engage in natural theology as anything other than intellectual capitulation. Hard-headed philosophers have little patience with appeals to the religious imagination as somehow decisive regarding religious claims such as the existence of God or the afterlife. But when logical arguments for God's existence are proffered, they leap into battle, eager to show that reason can strike the decisive blow. Besides Bertrand Russell, Anthony Flew (now an octogenarian) was probably the most prominent philosophical defender of atheism in the 20th century. While not as famous (or infamous) as Russell, Flew defended atheism more systematically and repeatedly than Russell, who wrote little more than his famous Why I Am Not a Christian.

Flew notably contributed his essay "Theology and Falsification" to the 1955 volume New Essays on Philosophical Theology, published when natural theology had probably reached its nadir in the Western world. His book God and Philosophy, published in 1966, was a rigorous if somewhat ponderously stated analysis of the meaning of theological language, the cogency of natural theology, and the credentials of divine revelation. Flew rejected fideism as intellectual decapitation, and inspected the best arguments he could find in support of God's existence. He claimed that the theist bore the burden of proof in these arguments, since the material world is clearly real, while the spiritual world (if it exists) is not. (He later called this "the presumption of atheism.") He had grave doubts that talk of a disembodied agent such as God made much sense, since all our notions of actions performed by persons rely on empirical factors not applicable to God. (Of course, if mind/body dualism is defendable, then we have plenty of good evidence for immaterial agents being real, since we are among them.[3]) Nevertheless, he investigated the constructive case for God by subjecting ontological, cosmological, design, and moral arguments to philosophical analysis. All failed to carry conviction, he argued. The claims of divine revelation fared no better.

Flew's work became a fixture in the philosophy of religion and a treasured resource for many atheists. Natural theology was dead; therefore, theism was intellectually bankrupt. Flew, an expert on David Hume, carried on the skeptical work that Hume had advanced in the 18th century. But Flew did not rest on his laurels. As part of a prolific career of publications, he debated evangelical philosopher and resurrection expert Gary Habermas concerning the resurrection of Jesus in 1987 and again more recently.[4] Flew remained unconvinced, but honestly interacted with Habermas' strong evidential case for the resurrection in both debates. Moreover, Flew debated William Lane Craig on the existence of God.[5] Despite Craig's carefully constructed  argument for God, the debate did not end with Flew on his knees. Yet in the last several years, I began to hear strange, hopeful rumors: Flew had converted to theism!

In 2005, Philosophia Christi released an online interview of Flew by Gary Habermas, in which Flew acknowledged that recent, scientifically oriented arguments from design had indeed convinced him of the existence of a designer outside of nature. However, Flew denied becoming a Christian. He was more of a deist, and did not believe in the afterlife. (Flew researched the paranormal early in his career, concluding that human "survival" was untenable.[6])

Many skeptics and atheists were stunned. Some doubted what they read. When Prometheus Books announced a reissue of God and Philosophy with a new introduction by Flew, many anticipated that the record would be set straight. However, the result was somewhat anticlimactic. The original text of the book was unchanged since its original publication in 1966. The failure to revise meant that Flew did not interact with the flood of new, philosophically rigorous arguments for God's existence and the rationality of divine revelation that have appeared in the interim (some of which were mentioned above). But the hot item was the much-awaited introduction. Flew's comments are detached from any personal conversion to theism. Rather, he writes programmatically and somewhat elliptically that any successor to God and Philosophy must take into account several developments in philosophy, some friendly to theism and some unfriendly. On the friendly side, Flew mentions the fine-tuning argument for theism and the "argument from the order of nature to God as its Intelligent Orderer" made in Roy Abraham Varghese's The Wonder of the World: A Journey from Modern Science to the Mind of God. But Flew also claims that the "multiverse theory is now a leading view among cosmologists today" (a view that avoids the theistic implications of the standard Big Bang model)[7] and that "protobiologists" are now able to produce adequate naturalistic theories of how living things came from non-living matter. Flew's confidence in such theories exceeds their rational warrant, especially on the likelihood of the richly informational structure of life coming from nonlife, but he says very little about either one of them.

So, in the final analysis the latest (and Flew says the last) edition of God and Philosophy offered an ambiguous preface and an outdated (but historically significant) text. That hardly carried the debate to a new level, however much it might have frustrated die-hard atheists and tantalized Christians.

But this was not Flew's final word. Two years later, There Is a God (written with Roy Abraham Varghese, a longtime interlocutor) was released. This helps clarify Flew's positions and why he holds them. He begins with his intellectual autobiography and does not commence to defend his new views until page 88. But it is worth the wait, because Flew is willing to follow the evidence wherever it leads. He no longer takes the idea of God as a disembodied agent to be problematic, and he presents four reasons why he now embraces theism: the consistent and rational laws of nature, the fine-tuning of the universe, the origin of the universe at the Big Bang, and the organized, information-rich nature of life. Flew rejects the multiverse theory he toyed with in the new introduction to God and Philosophy as extravagant and desperate. He rejects atheistic accounts of the Big Bang as less rational than the theistic explanation that God was the creator. Flew argues that naturalism faces an insuperable philosophical problem in trying to coax life from non-life without a designing mind. Flew presents these arguments rather briefly and without the kind of rigor that many philosophers might desire. Nevertheless, he lucidly makes his case, presents many salient points and apt illustrations, and gives references to other sources for further study.

Although Flew unambiguously argues that "there is a God," he makes no confession of Christian faith and denies the afterlife. He affirms that his intellectual journey has been guided by reason, not by faith. Reason has now led him to believe in an omnipotent God, who could reveal himself personally. The book concludes with a "dialogue" between Flew and the New Testament scholar N. T. Wright, in which Flew claims "that the Christian religion is the one religion that most clearly deserves to be honored and respected." Flew then explains the basic reasons he has given for not accepting Jesus as the self-revelation of God. He gives Wright 26 pages to argue for the history of Jesus, his identity as "the embodiment of the God of Israel," and for his resurrection. Flew concludes by writing that he finds Wright's arguments "impressive" and "fresh." Flew says he is open to hearing God's voice. I hope and pray that the Logos (John 1:1) will continue to speak to him.

In November 2007, The New York Times Magazine published an article suggesting that the aging Flew had been manipulated by Christians (particularly co-writer Varghese, who was responsible for the actual writing of the text), who wanted him to appear in the book to be more convinced of theism than he really was.[8] Even if this were so, the arguments stated would stand on their own merit. In any case, it seems unlikely that Flew, his family, and his publisher would have allowed such an egregious exploitation. Moreover, Flew has published statements on the Internet denying any foul play concerning the contents of There Is a God. Instead of a literary hijacking of an aging and enfeebled atheist by solicitous Christians, what we are faced with is an intellectual conversion of great significance.

William Lane Craig and Walter Sinnott-Armstrong's God? A Debate Between a Christian and an Atheist will not disappoint readers in search of stimulating contemporary debate over God's existence. Although the book is introductory, the philosophers take the reader into deep waters. Craig first presents the case for God, receives rebuttal by Sinnott-Armstrong, and then responds to the rebuttal. The order is reversed in the second section.

Instead of developing one theistic argument in detail, Craig advances five short arguments, providing a brief cumulative case argument that aims to secure several divine attributes. He begins with the kalam cosmological argument, which has a simple deductive form: (1) Whatever begins to exist has a cause of its existence. (2) The universe began to exist. (3) Therefore, the universe has a cause.

To make his case, Craig must explore the nature of the infinite. An actual infinite is a set of items that is literally limitless. But the concept of the actual infinite generates contradictions. For example, if you subtract all the odd numbers (1, 3, 5, … ) from the set of natural numbers (0, 1, 2, 3, … ) you are still left with an infinite number of numbers. Thus, infinity minus infinity equals infinity. But if you subtract all the numbers greater than two, you are left with three numbers. By this reckoning, infinity minus infinity equals three. Craig comments: "In both of these cases we have subtracted identical quantities from identical quantities and come up with contradictory answers. In fact, you can get any answer you want from zero to infinity. This implies that infinity is just an idea in your mind, not something that exists in reality." Thus the actual infinite exists only in the mathematical world,[9] not in the real world of space and time. Consequently, the number of past events cannot be actually infinite; it must be finite. So, the world must have a beginning. Furthermore, the beginning of the universe is scientifically confirmed through Big Bang cosmology, which claims that the universe exploded into existence out of nothing about 15 billion years ago. Since it is illogical to think that the universe—or anything—could pop into existence without a cause, Craig infers that the cause of the universe was a timeless "personal agent who freely chooses to create an effect in time without any prior determining conditions."

Craig offers four more crisp arguments: the existence of God gives the best explanation for: (1) the fine-tuning of the universe, (2) the existence of objective moral values, and (3) the life, death, and resurrection of Jesus. This makes Craig's argument specifically Christian and not merely theistic in a general sense. He concludes by arguing that (4) "God can be immediately—and without argument—known and experienced as 'properly basic.'" He also warns: "We mustn't so concentrate on the proofs for God that we fail to hear the inner voice of God speaking to our own heart."

Sinnott-Armstrong responds in the tradition of Hume by claiming that even if Craig's arguments succeed, he has not established the existence of an all-good, all-powerful, all-knowing, eternal, effective, and personal God.[10] In fact, the creator, the designer, and the moral lawgiver may be different finite beings. He substitutes naturalistic explanations for all the data from which Craig derives theistic explanations. He responds to the kalam argument by claiming that the actual infinite is commonly employed in transfinite mathematics and poses no problems. He disputes Craig's interpretation of the Big Bang by invoking other speculative possibilities that do not require an ex nihilo creation. And he finds it extremely implausible that a timeless and changeless cause (God) could effect a change at the beginning of time (the creation of the universe).

Craig rebuts Sinnott-Armstrong by defending his cumulative case approach, which collects several important theistic attributes from several different arguments. If successful, these arguments establish a being who is a personal Creator, uncaused, eternal, changeless (at least sans creation), immaterial, enormously powerful, inestimably intelligent, concerned with his creatures, good and loving, who exists by metaphysical necessity, is the God and Father of Jesus Christ, and is knowable. Craig does not directly critique the claim that each argument may refer to different deities. But Sinnott-Armstrong's charge seems ill-advised, since the divine attributes won through Craig's arguments are those classically affirmed by monotheism. An argument for polytheism would look quite different. Further, one should not multiply entities beyond what is required for a simple and sufficient explanation.

Craig seems to come out on top concerning the origin of the universe. He responds by reiterating that while actual infinites are allowed in transfinite mathematics, this is an abstract, conceptual discourse that abides by certain artificial rules, and that the actual infinite cannot exist in space-time reality. (Craig usually drives this home by arguing that even if an actual infinite exists, it could not be traversed in time—that is, produced through successive addition—since there would always be an infinite distance left to travel. But he does not make that point here.) Craig also convincingly counters that the alternatives to Big Bang cosmology presented by Sinnott-Armstrong are either outdated or too avant-garde to refute his arguments. While Craig defends the idea that a timeless being can produce an act in time—an argument I have never found persuasive—he also admits the possibility that God existed in "undifferentiated metaphysical time" prior to the creation, a view that fits with the kalam's conclusion and deflects the claim that the timeless cannot create something in time.

Sinnott-Armstrong marshals a threefold argument against God. He claims that the existence of certain types of evil are incompatible with the existence of an all-good and all-powerful God; that an eternal God could not produce effects in the temporal world; and that the prevalence of unbelief does not comport with the existence of a God who supposedly wants to be known. The last issue is a subset of the problem of evil (sometimes called "the hiddenness of God" objection). His first argument seems the most challenging.

In his response to Craig's moral argument for God, Sinnott-Armstrong (rather unconvincingly) affirms that moral propositions such as "rape is wrong" are true without further justification. This is pivotal to his argument against God, because without the existence of objective moral properties, the problem of evil cannot get off the ground. Sinnott-Armstrong builds a thorough argument from evil against God by critiquing each of ten possible strategies for justifying evils (such as the compensations of heaven, that suffering may produce better character, and so on). He limits his selection of evils to natural evils (such as infant deaths), so that the free-will defense cannot directly address them. His arguments are nuanced, thorough, and impressive. They attempt to put a crushing burden of proof on the theist to show that all evils are adequately compensated by some good that could not occur without them. For Sinnott-Armstrong, if any evil is uncompensated or pointless, this counts decisively against the existence of an omnibenevolent and omnipotent God, who surely would justify any evil that God allows. Sinnott-Armstrong grants that some evils are compatible with God's existence, but not the kinds he discusses.

Craig retorts by arguing that a combination of possible justifications for evils may cover all of them, even natural evils affecting innocents. In this way he sketches a positive theodicy, instead of merely charting a defense that would only render the existence of God and evil logically possible. However, Craig rightly notes that given our finitude, we cannot identify the reasons for every particular evil. Sinnott-Armstrong claims in his response that the mere possibility of these justifications offers a much less plausible argument than the idea that actual evils are simply inadequately compensated for.

The nub of the argument over evil seems to boil down to Craig's argument: (1) If God exists, gratuitous suffering does not exist. (2) God exists. (3) Therefore, gratuitous suffering does not exist.[11] Craig's strategies for God's possible justification of evils are merely speculative unless one has previously made a strong argument for a metaphysically and morally thick theism through natural theology. That is, background knowledge weighs crucially here. Since Sinnott-Armstrong denies the success of Craig's arguments for God, Craig's explanation for evil rings hollow and desperate to him. But if one takes Craig's overall, fivefold case for God to be strong (as I do), this defangs Sinnott-Armstrong's objections. A transcendently intelligent, good, and powerful God would have a vast arsenal of reasons and strategies to employ with respect to justifying evils. Since Craig argues forcefully—if briefly—for the resurrection of Jesus as part of the cumulative case for God's existence, it might have served him well to invoke Jesus' resurrection as part of the solution to the problem of evil as well. If Jesus has been raised victorious over death and sin, the world is not without hope. Evil does not have the last word.

While Christians believe that God will have the last word, the arguments for and against God's existence will likely continue apace until then. As for me and my house, we will continue to hold up our side of the debate.

Douglas Groothuis is Professor of Philosophy at Denver Seminary and co-editor (with James Sennett) of In Defense of Natural Theology (InterVarsity Press, 2005).

1. But Greek philosophy, even in its most theistic modes, never affirmed the creation of the universe out of nothing, as does the Bible.

2. In The Science of God (Eerdmans, 2004), pp. 71-91, McGrath redefines natural theology so as to remove the possibility that it provides evidence for the existence of God independent from the Bible. This move is both theologically novel and philosophically suspect. For another view of natural theology (or theistic proofs), see Douglas Groothuis, "Theistic Proofs," in New Dictionary of Christian Apologetics (InterVarsity Press, 2005), pp. 698-703.

3. For a careful defense of mind-body dualism, see J.P. Moreland and Scott Rae, Body and Soul (InterVarsity Press, 2000).

4. Terry Miethe, ed., Did Jesus Rise From the Dead? The Resurrection Debate (Harper and Row, 1987); John Ankerberg, ed., Resurrected? An Atheist and Theist Dialogue (Rowman & Littlefield, 2005).

5. San Wallace, ed., Does God Exist? The Craig-Flew Debate (Burlington, VT: Ashgate, 2003).

6. This was subsequently published in Philosophia Christi, new series, Vol. 6, No. 2 (2004), pp. 197-212.

7. For a critique of this view see Paul Copan and William Lane Craig, Creation out of Nothing: A Biblical, Philosophical, and Scientific Exploration (Baker Books, 2004), pp. 232-233; 238-240.

8. Mark Oppenheimer, "The Turning of an Atheist," The New York Times Magazine, November 4, 2007, www.nytimes.com/2007/11/04/magazine/ 04Flew-t.html

9. How the actual infinite functions in the world of mathematics is contested as well, as Craig and Sinnott-Armstrong note.

10. For a recent volume that critiques this and other Humean moves against natural theology, see James Sennett and Douglas Groothuis, eds., In Defense of Natural Theology (InterVarsity Press, 2005).

11. Some Christian philosophers, such as Michael Peterson, Keith Yandell, and William Hasker, believe that the existence of God and the existence of gratuitous evils are compatible, but Craig does not address this.

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