The Great Debate, God or Blind Nature? Philosophers Debate the Evidence, aims to bring together nine distinguished philosophers in a series of four debates, each with a different focus on evidence for and against naturalism and theism. The first debate addresses evidence concerning the nature of the mind and the will as it relates to the truth of naturalism and theism. The second debate introduces an argument from evil informed by evolutionary biology and considers whether evolutionary naturalism is self-defeating. The third debate appeals to the physical sciences, alternatively providing a cosmological argument against theism on the one hand and considering design arguments against naturalism on the other. The final debate revolves around why, if God exists, he remains hidden from so many people, and whether we should believe in God for practical reasons even in the absence of compelling evidence for his existence.
What sort of entity is the human mind? Also, what is freedom of the will, and do human beings have such freedom? Determining the correct answers to these questions is crucial for determining which of naturalism and theism is more credible.
Do the claims of evolutionary biology conflict with theistic religion? According to one very popular view, when properly conducted science and religion never conflict because they are isolated within separate domains. Another position is that evolution and theistic religion are in some fairly straightforward way logically incompatible. Are certain facts of evolutionary biology better explained on the hypothesis that naturalism is true, or on the hypothesis that theism is true?
According to conventional religious wisdom, if there is no God, then the existence of the universe is just a big accident--a "brute fact" that has no explanation. According to conventional antireligious wisdom, Charles Darwin's Origin of Species put the last nail in the coffin for the argument from design. Quentin Smith takes on the first of these sacred cows, concluding that there is a coherent sense in which the universe explains itself, while Robin Collins takes on the second adage, concluding that the presence of life in the universe is much more surprising on naturalism than on theism.
Uncertainty about the existence of God is common, but what are the implications of such uncertainty? Is it not the case that a loving God would not leave us in the dark about her existence, and therefore God's hiddenness from large numbers of human beings constitutes strong evidence that a loving God does not exist? Or should we take the opposite tact, that it is most reasonable to affirm faith in God in the absence of certainty about her existence?
In his opening argument, Quentin Smith argued that universe explains its own existence, without remainder, even if the universe has a finite age, for the state of the universe at any particular moment is sufficiently caused by all of its preceding states. Since this complete explanation makes no reference to God, Smith argued, insofar as God is by definition a part of any complete explanation of the universe, God does not exist. In his response, Robin Collins cited the flight of a cannonball as a counterexample to Smith's line of reasoning, but the counterexample is not analogous; unlike the universe, the flight of the cannonball does not have a historically complete explanation in terms of earlier parts of that flight. Being charitable to Collins, however, it is possible that although the universe has no first moment in physical time, it may in some metaphysical time series, allowing one to make room for God in a complete metaphysical explanation of the universe. Smith's argument, then, might not demonstrate the nonexistence of God, but it nevertheless provides a probabilistic argument against the existence of God. And on Collins' own "likelihood principle," the fact that our best scientific theory of the origin and evolution of the universe supports a self-caused universe is much more likely on naturalism than on theism, and thus provides very strong evidence for naturalism over theism.
Robin Collins argues that three facts implicate a designer of the universe--that life depends upon the precise tuning of physical constants, that the laws of physics show evidence of beauty, and that the universe is intelligible. But Collins' case is pervaded by vague arguments which shift between defending theism specifically and defending a more generic design hypothesis. This provides the appearance of having all of the advantages of the generic design hypothesis, such as greater initial plausibility, while masking the implication that intelligent life is just as unlikely given design with unspecified motives as it is given "chance." If design is to provide us with any expectations at all about what the world would be like, Collins has to defend theism in particular throughout. Moreover, while on single-universe naturalism the existence of anything as impressive as human beings may be very unlikely, on theism the existence of intelligent beings as unimpressive and flawed as humans is also very unlikely. And given that human beings do exist, single-universe naturalism, but not theism, entails that they exist in this particular universe.
Paul Draper rightly argues that fine-tuning gives us no reason to believe in a generic design hypothesis that tells us nothing about the motives of the designer. He also correctly notes that "The Case for Cosmic Design" does not establish the existence of God; but it nevertheless offers evidence for the existence of God. Fine-tuning is more surprising under the naturalistic single-universe hypothesis than under theism, and thus constitutes evidence for theism over the naturalistic single-universe hypothesis. When all of the evidence is considered, whether theism is objectively more likely to be true than the naturalistic single-universe hypothesis is an open question that depends upon a difficult assessment of the prior epistemic probability of theism. Since there are independent motivations for believing theism apart from fine-tuning and other design evidence, that evidence counts in favor of theism even if we cannot show that theism is true. Moreover, unless we have good reason to believe that the existence of evil is very improbable under theism, the combination of the fine-tuning data and the existence of evil supports theism over the naturalistic single-universe hypothesis. It is reasonable under the theistic hypothesis to think that the existence of limited, vulnerable moral agents is an overall good despite the evils that almost certainly would accompany the existence of such agents.
Paul Draper criticizes Alvin Plantinga's argument that since unplanned evolution is not likely to produce trustworthy cognitive faculties, evolutionary naturalists cannot rationally believe anything--including naturalism itself. Draper contends that this argument rests on a crucial but faulty inference from the premise that the probability that our cognitive faculties are reliable given unplanned evolution is low or inscrutable. The conclusion that evolutionary naturalists cannot rationally believe in unplanned evolution does not follow from this "probability thesis." If the thesis were amended to claim that the probability of reliable cognitive faculties given unplanned evolution is low (as opposed to "low or inscrutable"), then it would follow that naturalists cannot trust their cognitive faculties; but this amended thesis is demonstrably false, and thus Plantinga's evolutionary argument against naturalism fails.
Paul Draper's critique of the evolutionary argument against naturalism (EAAN) alleges that it does not follow from the probability thesis that evolutionary naturalists cannot rationally believe in unplanned evolution, but that this conclusion does follow from the amended but demonstrably false thesis that the probability of reliable cognitive faculties given unplanned evolution is low. Though Plantinga disputes that the probability thesis does not entail this conclusion, he does not take up that argument here. Rather, he aims to show (contra Draper) that the probability of reliable cognitive faculties given unplanned evolution is indeed low, given that evolution selects only for "indicators," not full-fledged beliefs. If evolutionary naturalism is true, then both true and false belief content will yield equally adaptive behavior, and thus natural selection will not select for true belief content over false belief content; but then naturalism is indeed self-defeating in the sense that naturalists cannot trust the cognitive faculties that lead them to believe that naturalism is true.
In this chapter, Paul Draper appeals to natural selection in order to show that the failure of many humans and animals to flourish is strong evidence against the existence of an omnipotent, omniscient, and morally perfect God. Treating theism and naturalism as hypotheses that aim to explain certain features of our world, Draper sets out to test each hypothesis against various known facts, including facts about human and animal suffering. After demonstrating that, prior to such testing, naturalism is more probable than theism in virtue of its smaller scope and greater simplicity, Draper goes on to argue that naturalism has far greater "predictive power" than theism, concluding that this provides strong grounds for rejecting theism.
Paul Draper argues that all else held equal, "naturalism is much more probable than theism," and therefore "theism is very probably false"; moreover, naturalism is simpler and smaller in scope than theism, and has much greater predictive power than theism with respect to evolutionary facts about suffering. In this response, Alvin Plantinga disputes that theism has larger scope than naturalism, and argues that what is really at issue for epistemic probability is not simplicity as Draper understands it (as "uniformity"), but "epistemic naturalness"--and that theism is more epistemically natural than naturalism. Moreover, if we treat theism as a hypothesis (rather than as a fact), theism might be subject to prima facie defeat by facts about suffering and misery, but nevertheless explain or predict a whole range of other data better than naturalism, such as our possession of reliable cognitive faculties, the existence of objective morality, the fine-tuning of the universe, the existence of abstract objects, and so on. But if some theists know that theism is true (in virtue of religious experiences, say), then their theism is not subject to defeat by facts about suffering even disregarding these explanatory advantages.
Alvin Plantinga does not challenge (and thus implicitly concedes) the soundness of Paul Draper's argument for the conclusion that certain facts about good and evil are strong evidence against theism. Plantinga does, however, challenge Draper's view that naturalism is more plausible than theism, which Draper needs to reach the further conclusion that, other evidence held equal, theism is very probably false. In addition, Plantinga challenges the significance of this final conclusion. In this chapter, Draper defends his views on plausibility and then argues that Plantinga's challenge to the significance of his final conclusion fails for two reasons. First, Plantinga fails to show that this further conclusion does not threaten the rationality or warrant of most theistic belief. Second, he mistakenly assumes that, in order to be significant, this conclusion must threaten the rationality or warrant of most theistic belief.