Faith and Reason Part 7: Plantinga, Continued

Mark Hansard continues his series on Faith and Reason, exploring a key twentieth- and twenty-first century philosopher. For the previous entries in the series, and other work by Mark, click here.

In my last entry, I introduced Alvin Plantinga, listed some of his contributions to analytic philosophy, and described his view of Reformed Epistemology. In this entry, we will look briefly at his evolutionary argument against naturalism.[1]

Several thinkers in the 20th Century, including C. S. Lewis, have described some version of this argument.[2] Lewis famously stated:

Unless we can be sure that reality in the remotest nebula or the remotest part obeys the thought laws of the human scientist here and now in his laboratory—in other words, unless Reason is an absolute—all [science] is in ruins. Yet those who ask me to believe this world picture also ask me to believe that Reason is simply the unforeseen and unintended by-product of mindless matter at one stage of its endless and aimless becoming. Here is flat contradiction. They ask me at the same moment to accept a conclusion and to discredit the only testimony on which that conclusion can be based.[3]

Plantinga has taken Lewis’ idea and the ideas of others and added philosophical rigor.

The first part of the evolutionary argument against naturalism[4] is based on Plantinga’s definition of warrant. As we saw in part 6, our beliefs have warrant when they are formed under the correct belief-forming mechanism which was triggered in the correct way, according to God’s design plan. Our warranted beliefs constitute knowledge when they are formed in this way and they are true. Three things to note about Plantinga’s definition of warrant: First, it includes a divine design plan. The reason our beliefs can constitute knowledge is that our faculties were designed to be triggered in the correct way to be able to ascertain truth, and thus have knowledge. Second, Plantinga’s definition of warrant is normative, and thus applies to everyone. It does not, in fact, matter whether a person believes in warrant, or even that they know anything about it. They simply must have warrant in order to have knowledge.[5] Third, note that Plantinga does not create this notion of warrant in order to use it in this argument. Instead, it is the result of sustained argument in two volumes of his three volume set on warrant. In Warrant: the Current Debate he argues that all other theories of knowledge are inadequate, and in Warrant and Proper Function he describes in detail the only alternative, his theory of warrant.[6] Thus, Plantinga’s definition of knowledge, if correct, requires a proper-functioning mind and environment, a system which is designed in order for truth to be observed and believed. It therefore solves Lewis’ contradiction that, for example, scientists are using reason to come to conclusions, when the (naturalistic) evolutionary process which created their reasoning process is a random, non-rational process (and thus makes their conclusions worthless). There is no contradiction here if the origin of our noetic structure (our mental abilities) is rational, or the result of a rational mind. If Plantinga is correct in his bold move, naturalism is false, and thus evolutionary naturalism is false as well.[7]

Plantinga argues further that evolutionary naturalism is irrational to believe, regardless of whether it is true or false. He declares that if evolutionary naturalism is true, the probability that our noetic structures are reliable is either 1) very low or 2) low enough that we should be agnostic about their reliability.[8] He comes to this conclusion by explaining five ways in which, in naturalistic evolutionary processes, holding true beliefs has nothing to do with survival value, and thus our noetic structures would not be conducive to forming true beliefs. For example, he says that, in some cases in which our beliefs are causally efficacious and have adaptive value according to their contents, even then, such beliefs wouldn’t necessarily be truth conducive.[9] For example, a pre-historic man might survive because every time he sees a mountain lion he runs away. But he might run away for the wrong reasons: suppose he believes that he should always pet a mountain lion, but this is best done by running away. Or suppose he likes the idea of being eaten by a mountain lion,[10] but he runs away because he would prefer to be eaten by a bear (fortunately for him, there are no bears around). And so forth. His beliefs would be causally efficacious and help him survive, but they are false.

Other scenarios Plantinga explains: suppose again that your beliefs are causally efficacious, but that has nothing to do with the content of your beliefs. One example he cites: suppose you read a poem very loudly, so loudly that it breaks some glass. The poem is causally efficacious in that the glass broke. But it had nothing to do with the content of the poem. Any loud words would do. Thus, your beliefs have nothing to do with their efficacy.[11] Or, in another scenario, suppose evolutionarily, beliefs have absolutely nothing to do with behavior, so they have no function or purpose at all. In this case, evolution would reward adaptive behavior, but beliefs would be accidentally tied to the brain states of an organism; they would be epiphenomenal.[12] For example, the nervous system could have evolved in such a way as to not require higher thought at all to avoid a mountain lion. It could be purely reactive, like touching a hot stove and jerking your finger away. In this case, beliefs would have no purpose for physical survival, or evolutionary purpose at all. They would be completely invisible to evolution, and thus completely useless. That is a sketch of three of the five scenarios Plantinga discusses, and it briefly shows that many evolutionary processes would not result in a rational, truth conducive noetic structure.

If Plantinga is right about this, then it is irrational to trust our noetic faculties because the idea that they would be truth conducive (given evolutionary naturalism) is unlikely. Given all of the naturalistic scenarios, it is much more likely they have nothing to do with actually forming true beliefs. Since it is our noetic faculties that came up with the idea of evolutionary naturalism in the first place, it would be irrational to believe in it. Evolutionary naturalism itself is the grounds for demonstrating it is false or unlikely.

One objection to Plantinga’s argument is just to say that we already know that we have rational, truth conducive faculties from other (non-evolutionary) sources. We know that we engage in rational thought every day, and we make true conclusions. But, Plantinga says, this is a pragmatically circular argument. It gives a reason for believing our noetic faculties are efficacious, but the reason is only itself true if our noetic faculties are efficacious. [13] If I doubt my reasoning abilities, I can’t use those abilities to prove they are indeed reliable.

Thus, what Plantinga does with the evolutionary argument against naturalism is to show how irrational it is to believe in the very rational faculties that came up with idea of naturalism in the first place. The only alternative is to believe a mind designed our faculties in order to make them truth conducive, and thus, trustworthy. And if Plantinga is right about warrant, and it or something like it is the only alternative to other theories of knowledge that are irrational or unlikely, then having knowledge at all requires God’s design. Once again, Plantinga has moved the debate and changed the discussion, this time in both epistemology and the metaphysics of God’s existence.


[1] For the discussion here I am relying on J.P. Moreland and William Lane Craig, Philosophical Foundations for a Christian Worldview (Downer’s Grove, IL: InterVarsity Press, 2nd ed. 2017), 93-97. Plantinga’s main argument can be found in Warrant and Proper Function (Oxford: Oxford University Press, 1993), chapts 11-12.

[2] C.S. Lewis’ full argument is in Miracles (New York: McMillen, 1947), chapts 1-4. See also Richard Taylor, Metaphysics (Englewood Cliffs, NJ: Prentice Hall, 1963), 112-19. William Hasker, Metaphysics (Downer’s Grove, IL: InterVarsity Press, 1983). And see Victor Reppert’s update on Lewis’ argument in C.S. Lewis’s Dangerous Idea (Downer’s Grove, IL: InterVarsity Press, 2003).

[3] C.S. Lewis, “Is Theology Poetry?” in The Weight of Glory and Other Addresses (New York: Simon & Schuster, 1975), 103.

[4] Naturalism: “the philosophical belief that everything arises from natural properties and causes, and supernatural or spiritual explanations are excluded or discounted.” (Google Dictionary)

[5] That is, warrant is a necessary but not sufficient condition for knowledge. Note as well, with Plantinga’s definition of warrant, that he is not simply describing the usual way in which the human mind and body function. Warrant is not a statistical description of how human brains work, for example. It is something you must have, indeed you ought to have, if you have knowledge. Related to this is the idea that one cannot take a contingent process, like evolution (which is contingent because it could have not occurred), and use that in a definition for normative warrant, or some other type of normative justified belief. See Moreland and Craig, 94.

[6] Warrant: The Current Debate (Oxford, Oxford University Press, 1993), and Warrant and Proper Function (Oxford: Oxford University Press, 1993). The third volume is Warranted Christian Belief (Oxford: Oxford University Press, 2000).

[7] Again, this does not mean that evolutionary theory, per se, is false, only that atheistic version(s) of evolution are false. Plantinga actually argues that evolutionary biology is consistent with design. See his “Evolution and Design,” in For Faith and Clarity, ed. by James K. Beilby (Grand Rapids, MI: Baker Academic, 2006), chapt. 9.

[8] Moreland and Craig, 94.

[9] Ibid., 95-96.

[10] Ibid., 96.

[11] Ibid., 95.

[12] Ibid., 94-95.

[13] Ibid., 96.

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Mark Hansard

Mark is on staff with InterVarsity Christian Fellowship in Manhattan, Kansas, where he ministers to Faculty at Kansas State University and surrounding campuses. He has been in campus ministry 25 years, 14 of those years in faculty ministry. He has a Master's degree in philosophy and theology from Talbot School of Theology, La Mirada, CA, and is passionate about Jesus Christ and the life of the mind. Mark, his wife and three daughters make their home in Manhattan.

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