Darwins Doubt Part II

Continued from : here

The question before us is ... does naturalistic evolution give us reason to doubt that our cognitive faculties produce mostly true beliefs? I need to throw in some probability syntax to proceed.

Plantinga references Professor Churchland's formulation of the probability of the proposition that our cognitive faculties are reliable given naturalism and evolution ... as : P(R/N&E), where 'R' is the proposition that our cognitive faculties are reliable, 'N' the proposition that naturalism is true, and 'E' the proposition that we have evolved according to the suggestions of contemporary evolutionary theory. Darwin's "horrid thought" was that the probability was low.

I will abbreviate N+E to mean naturalism-is-true-and-we-evolved-the-way-that-Darwinists-claim-we-did ... it is shorter and easier to write ;-)

What is the relationship of belief to behavior? To venture a stab at this, we need to consider all of the possibilities. There are four mutually exclusive and jointly exhaustive possibilities.

Possibility one (P1): Epiphenomalism. I posted on this recently here: . Epiphenoma are side effects. This theory posits that beliefs are side effects of the brain. The electro-chemical properties of the brain drive behavior ... and beliefs are by products. This is a popular view among naturalists because it leaves no room for things like souls to exist. If P1 is true, then the probability of N+E producing reliable cognitive faculties is low. Why? Because the content of your belief ... whether it is true or false ... makes no difference at all. Stated differently, your beliefs are invisible to natural selection ... which only cares about your behavior.

Possibility two (P2): Semantic epiphenomenalism: it could be that their beliefs do indeed have causal efficacy with respect to behavior, but not by virtue of their content. This is odd, in my opinion, but a possibility. This possibility asserts that the truth or falseness of the belief is not what counts. What counts is how the brain fires neurons, the rate, the strength, the firing thresholds etc. It just so happens, that the firing of these patterns has causal efficacy on behavior ... in other words, the brain activity of having a random belief enhances survival. P(R/N&E) if P2 is true? Low. Very low. Beliefs could be false and it make no difference to natural selection.

Possibility three (P3): Beliefs are causally efficacious towards behavior, but in a maladaptive one. In other words, beliefs matter, but they hurt you. P(R/N&E) if P3 is true? Low. Very low.

Possibility four (P4): Beliefs are causally connected to behavior and adaptive. There is one problem, tho. Beliefs get mixed in with desires (fear – suspicion – doubt – approval – disapproval ) and the combination is what affects behavior. There are many possible belief-desire combinations. Perhaps a belief is false, but the desire causes fitness enhancing behavior anyway. Untrue beliefs paired with bizarre desires could be more adaptive than true beliefs. P(R/N&E) is P4 is true? High. But not sky high.

The probability calculus with weighting looks like this: P(R/N&E) = (P(R/N&E&P1) x P(P1/N&E)) + (P(R/N&E&P2) x P(P2/N&E)) + (P(R/N&E&P3) x P(P3/N&E)) + (P(R/N&E&P4) x P(P4/N&E)).


When I first saw this, I got heartburn. It is not as complicated as it first appears. Bascially it means this. The probability of N+E producing beliefs that are mostly true will be the weighted average of the four possible scenarios. We have already established the probabilities of N+E producing true beliefs for each scenario: very low, very low, very low and high but not sky high.

Now, we need to assign probabilities to the likelihood of each of the scenarios (P1 => P4) being true. Since these four scenarios are exhaustive, the probability that one them is true is 1 (or 100 percent).

Here is the kicker. A naturalist is going to want to argue for epiphenomalism. He does not believe in mind over matter. He believes that mind is matter. Beliefs, which are part of the mind, are really side effects (epiphenomena) of neural activity. The odds of P1 or P2 being likely are at least fifty-fifty or higher, one would think. This would put the odds of P4 being true at less than fifty-fifty.

Do you see the problem? The only scenario which may produce reliability in our beliefs is P4 ... which is itself not a slam dunk because of desire-belief combinations. Still, if this is only likely around half of the time, then one can clearly see what is going to happen to our weighted average for P(R/N&E)... it will be low.

Conclusion, the probability of natural selection producing true beliefs is low ... hence, Darwin's nagging doubt.

Even if you say ... horse feathers on all this nonsense ... no one really know the probability. That leaves you with two possibilities ... that the probability is unscrutable or that it is low. Darwin's doubt remains.

This argument is an undercutting defeater against naturalistic Darwinism being true. What is more, it is an UNDEFEATABLE defeater ... it cannot be defeated. Why? Because if N+E were true, then all beliefs are suspect and unreliable ... including the belief that this Darwin's doubt argument is bunk.

I think that is some interesting brain candy to snack on, don't you?


Weekend Fisher said…
Hi there

I'd think the most obvious response would be "we humans aren't all that rational." The people I talk with routinely display high levels of irrationality, imperviousness to facts, resistance to change, and so forth.

Another way you could interpret your probability equation would be as a probability that *any given thought* is caused by that type of phenomenon. This interpretation would give an understanding that our various thoughts are split percentage-wise amongst causes (and may share causes).

Darwinists could surely use to their advantage a few facts: That self-interest seems to rank high amongst the observable causes of our thoughts; that desire to engage in reproductive behavior no matter what the consequences also seems to rank high in the underlying causes of self-interested thoughts.

Or as C.S. Lewis might have said by the mouth of Lucy, "What if people started going all wild inside?"

Take care & God bless

Popular posts from this blog

Where did Jesus say "It is better to give than receive?"

How Many Children in Bethlehem Did Herod Kill?

Martin Luther King, Jr., Jesus, Jonah and U2’s Pride in the Name of Love

Dr. John Lennox: Video - Christmas for Doubters

On the Significance of Simon of Cyrene, Father of Alexander and Rufus

William Lane Craig on "If Mind is Reducible to Brain Function, Why Trust Thought?"

The Meaning of the Manger

Responding to the “Crimes of Christianity”; The Inquisition

Fine Tuning Bait and Switch