INTRODUCTION 

This is the first article in a series on how one might offer several different moral arguments that all (1) focus on our knowledge of moral truth and (2) reinforce each other so that their joint force is even stronger than the force of each individual argument.[1] There are different kinds of moral arguments for the existence of God. Some aim to show that God is needed for objective moral truth to exist; others focus on the advantage that God offers for justifying other aspects of morality, such as: moral knowledge, moral transformation, or moral rationality. This series of articles focuses specifically on three well-known arguments for God’s existence that have to do with our moral knowledge. I will make the case that these arguments, while different, are complementary. After examining each argument, the series concludes by offering a strategy for how they can be used in conjunction so that they reinforce each other. In this first article of the series, I examine Mark Linville’s “Argument from Evolutionary Naturalism” (AEN), which is similar to an argument given by Alvin Plantinga.

THE ARGUMENTS OF MARK LINVILLE AND ALVIN PLANTINGA 

Mark Linville’s AEN is a deductive argument which aims to show that naturalism is false because evolutionary naturalism (EN) undermines any basis for humans having moral knowledge, yet we seem to have moral knowledge.[2] Since Darwinian evolution is the “only game in town” for naturalists in terms of accounting for the diversity of biological life, Linville justifiably lumps evolution and naturalism together.[3] Linville is hardly the first to make the claim that EN cannot justify moral knowledge; many secular ethicists recognize this,[4] and a number of theists, like Linville, have also reached this conclusion—perhaps none more notable than Alvin Plantinga. Let us first examine Linville’s argument and then compare it with Plantinga’s. Linville argues:

(1) If EN is true, then human morality is a by-product of natural selection.

(2) If human morality is a by-product of natural selection, then there is no moral knowledge.

(3) There is moral knowledge.

(4) Therefore, EN is false.[5]

Premise (1) contends that through the process of natural selection we have evolved with a sort of programming to hold moral beliefs that are conducive to survival. Morality is crucial to our “survival and reproductive success,” so we cannot think it is independent of natural selection. All rational moral deliberation must be within the boundaries of that programming.[6] Linville points out that Darwin himself held that our moral programming would have been much different had we evolved under different conditions; if humans had evolved under the sort of conditions in which hive-bees evolved, then “there can hardly be a doubt that our unmarried females would, like the worker-bees, think it a sacred duty to kill their brothers, and mothers would strive to kill their fertile daughters, and no one would think of interfering.”[7] If EN were true, we surely could not escape the bounds of our evolutionary moral programming. So we should accept (1).

Premise (2) recognizes that just because our moral beliefs help us to survive, that does not require that the beliefs track any moral truth. The evolutionary processes involved in the development of our moral beliefs are independent of these beliefs being true, and if EN were true then a plausible account of our moral beliefs can be given by appealing to the survival value of us holding them.[8] This means that “our moral beliefs are without warrant” and “do not amount to knowledge.”[9] By contrast, a theist can appeal to God’s design of our minds to recognize moral truth, providing a basis to justify our moral knowledge. Premise (3) holds that we do seem to have genuine moral knowledge, thus (4) concludes that EN is false.

Alvin Plantinga’s argument is slightly different. While Linville argues that, if EN were true, our moral knowledge would be aimed at adaptiveness for survival, Plantinga emphasizes the adaptiveness of our behavior and argues that all of our beliefs are unimportant apart from their being consistent with adaptive behavior. In a world where EN is true, our beliefs essentially go along for the ride, and their truth or falsity makes no difference so long as they do not get in the way of adaptive behaviors. Plantinga’s argument is that we have reason to doubt the reliability of our “cognitive faculties” (e.g., memory, perception, sympathy, introspection, induction, moral sense).[10] What EN ensures is that we behave in ways that lead to survival and reproduction; thus, the role of our cognitive faculties is not producing true beliefs, but instead “contributing to survival by getting the body parts in the right place.” Natural selection guarantees adaptive behavior, but why think our cognitive faculties produce true beliefs?[11]

Plantinga’s argument goes as follows. Premise (P1) holds that “the conditional probability that our cognitive faculties are reliable, given [EN], is low.”[12] Premise (P2) is that “anyone who accepts (believes)” EN and also realizes that (P1) is true “has a defeater for” thinking that her cognitive faculties are reliable.[13] Premise (P3) then states that “anyone who has a defeater for [the reliability of her cognitive faculties] has a defeater for any other belief she thinks she has, including [EN] itself.”[14] (If one’s cognitive faculties are unreliable, then all beliefs produced by them—which are all of one’s beliefs—are unreliable.) Finally, Premise (P4) concludes that: “If one who accepts [EN] thereby acquires a defeater for [EN], [EN] is self-defeating and can’t be rationally accepted.”[15]

Clearly (P1) is the crucial premise. Linville notes that many intuitively find Plantinga’s first premise implausible because “the link between true belief and adaptive behavior” seems credible when it comes to nonmoral behaviors, such as hunting for food. Linville prefers the more modest claim that EN only calls into question our moral beliefs because the adaptive success of many nonmoral behaviors seem to be tied to the truth of our beliefs.[16]

Despite Linville’s concern, Plantinga makes a solid case for P1. Plantinga recognizes that most of us assume our cognitive faculties are mostly reliable. But “the naturalist has a powerful reason against this assumption, and should give it up” if he also accepts evolution. When a frog eats an insect, it does not matter what the frog believes or whether those beliefs are true so long as the frog engages in the right behavior to eat the insect and thus survive.[17] In response to the sort of concern raised by Linville that “true beliefs will facilitate adaptive action” better than false beliefs, Plantinga agrees but contends that it is “irrelevant” because “we are not asking about how things are, but about what things would be like if both evolution and naturalism (construed as including materialism) were true.”[18] Plantinga is not arguing that our cognitive faculties are unreliable in the actual world; he is only arguing that they would be unreliable if EN were true. Moreover, no test could demonstrate the reliability of one’s cognitive faculties because such a test would require the use of one’s cognitive faculties. Plantinga rightly concludes that “this defeater, therefore, can’t be defeated.”[19]

If Plantinga’s argument succeeds, then it expands the scope of the knowledge problem faced by EN beyond Linville’s argument: All of our beliefs are dubious. Next time, we will look at a second kind of moral knowledge argument.

1. These articles are adapted for a popular audience from an article that I published in the Journal of the International Society of Christian Apologetics (Volume 12, 2019, pp. 49-64) that is titled “Toward a Cumulative Epistemic Moral Argument for God’s Existence.”

2. Naturalism is the view that the natural world is all that exists (i.e., there is no God or supernatural realm). Evolutionary naturalism is the view that both naturalism and Darwinian evolution are true.

3. Mark Linville, “The Moral Argument,” in The Blackwell Companion to Natural Theology, eds. William Lane Craig and J. P. Moreland (Oxford: Blackwell Publishing Ltd., 2009), 392-395.

4. Ibid., 393. Secular ethicists such as E. O. Wilson and Michael Ruse have similarly concluded that EN reduces ethics to an illusion and requires that any belief we have that we are apprehending some real and objective moral truth is merely a “useful fiction” that has survival benefits.

5. Ibid., 394-398. On pages 397-398, Linville frames the argument he laid out on page 394 in epistemic terms by modifying Premises (2) and (3) to refer to “moral knowledge” rather than “moral facts.”

6. Ibid., 400-403.

7. Charles Darwin, The Descent of Man and Selection in Relation to Sex, 2nd ed. (New York: D. Appleton & Co, 1882), 99.

8. Linville, “The Moral Argument,” 394-398.

9. Ibid., 397.

10. Alvin Plantinga, Where the Conflict Really Lies: Science, Religion, and Naturalism (Oxford: Oxford University Press, 2011), 311-312.

11. Ibid., 315-316.

12. Ibid., 317.

13. Ibid., 340.

14. Ibid., 343.

15. Ibid., 344.

16. Linville, “The Moral Argument,” 408.

17. Plantinga, Where the Conflict Really Lies, 328.

18. Ibid., 335.

19. Ibid., 346.