The Evolutionary Argument Against Naturalism

This is a simplified presentation of Alvin Plantinga’s “evolutionary argument against naturalism”, written in May 2006 for an essay contest.

Synopsis

Originally constructed by Alvin Plantinga, this transcendental argument demonstrates that evolutionary naturalism is self-defeating. Contemporary evolutionary theory claims that our cognitive abilities evolved to help us survive. But this only ensures their ability in survival—not in truth. Since false beliefs can allow or produce beneficial behavior, the reliability of our beliefs is either low or inscrutable. Since naturalism is a belief, it is unreliable and therefore irrational. I will attempt to simplify and strengthen Plantinga’s argument by eliminating the use of Bayesian probability theory, more carefully defining types of thought, and providing better examples of false beliefs producing adaptive behavior. Furthermore, I will comment on the axioms necessary for justified true belief, which are found only in the Bible.

The Composition of Thoughts

Naturalism holds that matter and energy are all that exists. Therefore, even our thoughts are reducible to interactions between matter obeying fixed laws of chemistry. Since physical laws obey cause and effect, our thoughts are determined.1

What determines our thoughts? Although the motion of atoms is purposeless and irrational, something has orchestrated the atoms in our brain to produce rational thoughts.2

Evolution answers this question. Evolution, although blind, purposeless, and indifferent, produces organisms able to survive in an ecological niche. Therefore, our thoughts have been determined by evolution and have a value in survival. But how likely is it then that our thoughts are actually true? As neuroscience philosopher Patricia Churchland observed:

Boiled down to essentials, a nervous system enables the organism to succeed in the four F’s: feeding, fleeing, fighting, and reproducing. The principle chore of nervous systems is to get the body parts where they should be in order that the organism may survive … Improvements in sensorimotor control confer an evolutionary advantage: a fancier style of representing is advantageous so long as it is geared to the organism’s way of life and enhances the organism’s chances of survival. Truth, whatever that is, definitely takes the hindmost.3

In other words, Churchland recognizes that evolution only gives us reason to trust our thoughts in survival, not necessarily in truth. But W.V.O. Quine, philosopher and logician, claims that for this reason we have good reason to trust our thoughts:

There is some encouragement in Darwin. If people’s innate spacing of qualities is a gene-linked trait, then the spacing that has made for the most successful inductions will have tended to predominate through natural selection. Creatures inveterately wrong in their inductions have a pathetic but praiseworthy tendency to die before reproducing their kind.4

Quine is correct, depending on type of thought induced. Obviously if a creature’s cognitive faculties fail to detect the presence of a predator that creature will die shortly. This is basic perception. But is it the only type of thought? If not, what types of thought affect survival? Therefore, for the purposes of this essay, I shall categorize thoughts into three types: perceptions, valuations, and beliefs.5

Perceptions are mental constructs of objective reality, as detected by the senses. Their reliability corresponds to their accuracy. A basic example of perception is a bird that avoids eating a poison dart frog upon recognizing its bright colors. Another example is thirst. If I cannot recognize that my body needs water, I will certainly die.

Valuations are subjective, being opinions, attitudes, or desires. Some valuations are more important for survival than others, such as ‘I love you’ versus ‘Clarence is a beautiful name’.

Beliefs are explanations of our perceptions and valuations, therefore they have an objective truth value.6 Like perceptions, their reliability depends on their accuracy. Laws of nature, theorems, presuppositions, and worldviews are all beliefs.

The Doubt Developed

Thoughts by themselves do not infer a survival advantage, but rather must produce behavior that succeeds in performing Churchland’s four actions.7 Perceptions affect survival in an obvious way, causing us to act or react in a necessary way, therefore our perceptions must be reliable. If valuations affect our behavior, it must be in a positive way, therefore they must reflect desires beneficial to survival. And this is exactly what we find through our desire for food, sex, comfort, and so on. Beliefs, however, seem more complicated. Do beliefs directly affect behavior in some way, or indirectly by influencing valuations? Indeed, our valuations reflect our beliefs. Regardless, what is the relationship between beliefs and behavior? And what is the likelihood that true beliefs will evolve through this relationship? Some possibilities:

  1. Beliefs do not cause behavior, making them invisible to evolution—mere byproducts of the atomic motion of our brains. The likelihood of a creature having true beliefs, then, is probably low, but more importantly it would be inscrutable. Trusting these beliefs would be irrational, like trusting the accidental spelling of ‘New Zealand is north of Russia’ after a Scrabble board had fallen on the floor.
  2. To quote Plantinga, “beliefs do indeed cause behavior, but only by virtue of their electro-chemical properties, not by virtue of their content.”8 This possibility suffers the same fate as the first: the likelihood of evolution producing true beliefs is inscrutable.
  3. Beliefs do cause behavior by virtue of their content.9 Since creatures—or at least humans—are consciously aware of their beliefs and consciously choose their behavior, this possibility seems self-evident. If this behavior is adaptive, are the thoughts behind them necessarily true?

Consider a hypothetical hominid that dreadfully fears any dead creature. He may have this fear because he believes that contact with the dead will cause him to inherit that ‘property’—death—similar to how contact with water makes him wet or contact with a warm object makes him warm. This belief, while false, provides two adaptive behaviors. First, he is forced into a vegetarian diet, which is adaptive because fruits, vegetables, and nuts are more plentiful and accessible than game. Second, his chance of catching a disease is greatly reduced. Both of these adaptive behaviors improve his health, growing him into a strong and attractive mate, which allows him to produce more offspring.

Perhaps this hominid teaches his behavior to his offspring and this behavior is passed down through the generations as his progeny succeed in the local gene pool. The initial belief, however, is eventually lost over successive generations.

Is this scenario plausible? It is untestable. Consider then a scenario involving ourselves.

Over the past two thousand years, Christianity has thrived in many cultures. As of 2000, 34% of the world’s population claims to adhere to some form of Christianity.10 According to naturalists, Christianity would qualify as a meme—a “gene of the psyche”. In his book The Selfish Gene, naturalist Richard Dawkins writes, “Just as genes propagate themselves in the gene pool by leaping from body to body via sperms or eggs, so memes propagate themselves in the meme pool by leaping from brain to brain via a process which, in the broad sense, can be called imitation.”11 Some evolutionists say that humans have a genetic predisposition for Christianity, perhaps as part of a “god gene”12, whereas others may say that environment causes humans to accept Christianity. Regardless of which side is correct, one thing is for certain: many humans evolved to believe the falsehood of Christianity.

The Argument Against Naturalism

Therefore, since evolution produces false beliefs, we now have a defeater for the reliability of our beliefs—”a reason to doubt it, to be agnostic with respect to it.”13 The question arises, then, why should the naturalist trust his belief in naturalism?

The naturalist is presented with two options, both self-defeating to his position. He may first say that the probability of evolution producing true beliefs is high, because true beliefs have a greater tendency to produce adaptive behavior than untrue beliefs. If this is the case, then shouldn’t the naturalist accept Christianity, or at least theism, as true? Of course, if he does, he is no longer a naturalist. The other option—the option the naturalist is forced to take—is admitting that naturalism is possibly false. Now the burden is on the naturalist to demonstrate the validity of naturalism. In attempting to do this, the naturalist may claim that naturalism is a theory well informed by independent evidence, namely scientific evidence. This proves to be a futile justification, however.

First, it ignores the obvious metaphysical assumption of naturalism: “The Cosmos is all there is, or ever was, or ever will be”.14 This is an assumption because it rejects beforehand a non-naturalistic metaphysic and because it makes a claim about the universe that the naturalist cannot possibly know without being omniscient. A metaphysical assumption is not a natural phenomenon, therefore science cannot test it. Perhaps the naturalist will argue that since the natural world is all he can study, the natural world is all that can exist. But this is logically invalid.15 Therefore, any attempt to verify naturalism through science is question-begging or insufficient.

Second, since the naturalist’s presupposition is determined according to naturalism, his evidence can never be objective and therefore can never be independent. In other words, the naturalist cannot even help the fact that he believes naturalism, so why trust his obviously biased defense of naturalism?

Combine this inability to verify naturalism given its own epistemology with the naturalist’s determined bias, and the reliability of naturalism becomes completely inscrutable. Plantinga calls this an “undefeated defeater,” meaning that it is impossible to defeat the fact that the reliability of naturalism is inscrutable. To quote Plantinga, “[Naturalism] is therefore unacceptable and irrational.”16

The Foundation of Knowledge

While there is no encouragement in Darwin concerning the trustworthiness of our beliefs, there is much encouragement in God’s word. We can trust our truth-forming capabilities only because our minds are created in the image of a rational God. We can trust induction (and therefore science) because God upholds the universe in an orderly fashion. Furthermore, man does not create or discover truth, but rather a perfect, authoritative God who cannot lie reveals truth to man. Johannes Kepler stated this succinctly when he said, “O God, I thank Thee that Thou hast permitted me to think Thy thoughts after thee.”17 Indeed, any epistemology grounded in the authority of fallible man will ultimately reduce to skepticism and irrationalism. “Hath not God made foolish the wisdom of this world?” Truly, “the fear of the Lord is the beginning of knowledge” (Proverbs 1:7).

Notes and References

  1. Not necessarily pre-determined, due to the entropic motion of atoms, but nevertheless determined at that moment by chemical processes.
  2. This in itself is an argument against naturalism—why should the irrational motion of atoms result in a rational, ordered universe, let alone the ability for man to form rational thoughts? C.S. Lewis originally presented this argument, known as the Argument from Reason, in the third chapter of Miracles.
  3. Quoted by Plantinga. Planting, A., “An Evolutionary Argument Against Naturalism”, http://hisdefense.org/articles/ap001.html, May 11, 2006.
  4. Ibid.
  5. It should be noted that thoughts are related through logic—the reliability of which is another generous assumption given to the naturalist in this essay. The perennial problem of causality and induction as formulated by atheist David Hume rightfully demonstrates that naturalists cannot even trust their ability to induce.
  6. The formal philosophical definition of a belief is a mental state in which a proposition is affirmed. In this essay, perhaps a useful synonym would be “idea”.
  7. A case could be made for the necessity of adaptive behavior that extends beyond feeding, fleeing, fighting, and reproducing—the idea is adaptive behavior in general.
  8. Plantinga, A., “An Evolutionary Argument Against Naturalism”, http://hisdefense.org/articles/ap001.html, May 11, 2006.
  9. This is an ideal scenario for naturalism, since the relationship between beliefs and behavior could actually be a combination of 1, 2, and 3, in which case 1 and 2 would certainly contaminate the reliability of beliefs.
  10. “Major Religions of the World Ranked by Number of Adherents”, http://adherents.com/Religions_By_Adherents.html, May 11, 2006.
  11. Dawkins, R., The Selfish Gene, 1989 edition: Oxford University Press, 1989.
  12. “’God gene’ discovered by scientist behind gay DNA theory”, http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2004/11/14/ngod14.xml&sSheet=/news/2004/11/14/ixnewstop.html, May 11, 2006.
  13. Plantinga, A., “An Evolutionary Argument Against Naturalism”, http://hisdefense.org/articles/ap001.html, May 11, 2006.
  14. The famous words of the late Carl Sagan.
  15. To say that the universe is all that exists because the universe is all that science can study is to say that science is the only means of obtaining knowledge. This epistemology, known as scientific positivism (or scientism), is self-defeating. Epistemologies are ideas, not natural phenomena, therefore by scientific positivism’s own criterion it cannot justify itself.
  16. Plantinga, A., “An Evolutionary Argument Against Naturalism”, http://hisdefense.org/articles/ap001.html, May 11, 2006.
  17. Quoted by Tozer. Tozer, A.W., “On the Origin and Nature of Things”, http://www.worldinvisible.com/library/tozer/5j00.0010/5j00.0010.05.htm, May 11, 2006.