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Evolutionary Argument Against Naturalism: A Summary

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Alvin Plantinga’s evolutionary argument against naturalism is probably one of the most interesting arguments I have heard. Plantinga says this argument he formulated was inspired and somewhat derived from an argument by C.S. Lewis of the same sort of nature.

He first defines some key words used in the argument.
-Theism: The belief that there is an all-good, all-powerful, and all-knowing God. This God is personal and created the world.
-Naturalism: view that there isn’t any such a person as God. Nothing like God. A bit broader than atheism.
-Evolution: random genetic mutation worked on by natural selection and genetic drift.
-Cognitive faculties: “the powers or faculties of capacities whereby we have knowledge or form belief: memory, perception, reason, maybe others”

Only in creatures with reason and logic is there found an image of God.

“Since human beings are said to be in the image of God in virtue of their having a nature that includes an intellect, such a nature is most in the image of God in virtue of being most able to imitate God (ST Ia q. 93 a. 4)
Only in rational creatures is there found a likeness of God which counts as an image . . . . As far as a likeness of the divine nature is concerned, rational creatures seem somehow to attain a representation of [that] type in virtue of imitating God not only in this, that he is and lives, but especially in this, that he understands (ST Ia Q.93 a.6). -Saint Thomas Aquinas.”

Many people seem to believe that evolution and naturalism are compatible. But isn’t there a problem for the naturalist? Our cognitive faculties would have evolved from blind processes, genetic drift, and natural selection. This evolution process took billions of years.

Evolution does not care about true beliefs. All it cares about are feeding, fleeing, fighting, and reproducing. It rewards behavior that fall in line with these four things. But it does not guarantee truth in any way. Darwin himself had doubt about this. Darwin said, “the horrid doubt always arises whether the convictions of man’s mind, which has been developed from the mind of the lower animals, are of any value or at all trustworthy. Would any one trust in the convictions of a monkey’s mind, if there are any convictions in such a mind?”

This doubt, as Plantinga states, can be represented like this:
P(R/N&E)
P meaning probability.
R meaning the reliability of our cognitive faculties.
N&E meaning naturalism and evolution.

Plantinga goes on by figuring out the probability of the reliability of our faculties if naturalism is true. He does this through thought experiments, examining contemporary naturalistic views of the mind, and how evolution affects (or lack thereof) our beliefs. He finds the probability to be staggeringly low.

The summary of the core of his argument goes like this:
One who accepts N&E has a defeater for R (because of the probability). If you have a defeater for R then you have a defeater for any belief you have because any belief is a product of your cognitive faculties. But one of your beliefs is N&E. Therefore you shouldn’t accept naturalism as a rational position because it is self-defeating.

He says:
“One who contemplates accepting naturalism, and is torn, let’s say, between naturalism and theism, would reason as follows: if I were to accept naturalism, I would have good and ultimately defeated reason to be agnostic about naturalism; so I shouldn’t accept it. (An argument for the irrationality of naturalism, not for its falsehood.) The traditional theist, on the other hand, has no corresponding reason for doubting that it is a purpose of our cognitive systems to produce true beliefs, nor any reason for thinking the probability of a belief’s being true, given that it is a product of her cognitive faculties, is low or inscrutable. She may indeed endorse some form of evolution; but if she does, it will be a form of evolution guided and orchestrated by God. And qua traditional theist — qua Jewish, Moslem, or Christian theist – she believes that God is the premier knower and has created us human beings in his image, an important part of which involves his giving them what is needed to have knowledge, just as he does. The conclusion to be drawn, therefore, is that the conjunction of naturalism with evolutionary theory is self-defeating: it provides for itself an undefeated defeater. It is therefore unacceptable and irrational.”

This argument leaves the metaphysical naturalist in a very uncomfortable position that their belief in naturalism might be false due to the low probability of their cognitive faculties being reliable. This argument is sound and Plantinga delivers it effectively.

For a full text of the argument click here.

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