Where the Conflict Really Lies: Science, Religion, and Naturalism (40 page)

So much for an initial and rough statement of the argument; now we must proceed to develop it more carefully. The first premise, as I say, is something like the worry or doubt that our cognitive faculties would not be reliable if both naturalism and evolution (or perhaps just naturalism) were true. This worry has some eminent advocates. For example, there is Friederich Nietzsche. Ordinarily what Nietzsche says inspires little confidence, but in the following he may be on to something:

It is unfair to Descartes to call his appeal to God’s credibility frivolous. Indeed, only if we assume a God who is morally our like can “truth” and the search for truth be at all something meaningful and promising of success. This God left aside, the question is permitted whether being deceived is not one of the conditions of life.
⁸

To leap to the present, there is the philosopher Thomas Nagel, himself no friend of theism: “If we came to believe that our capacity for objective theory [true beliefs, e.g.] were the product of natural selection, that would warrant serious skepticism about its results.”
⁹
According to another philosopher, Barry Stroud (again, no friend of theism), “There is an embarrassing absurdity in [naturalism] that is revealed as soon as the naturalist reflects and acknowledges that he believes his naturalistic theory of the world…. I mean he cannot say it and consistently regard it as true.”
¹⁰
As Patricia Churchland, an eminent naturalistic philosopher, puts it in a justly famous passage:

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.
¹¹

Churchland’s point, clearly, is that (from a naturalistic perspective) what evolution guarantees is (at most) that
we behave
in certain ways—in such ways as to promote survival, or more exactly reproductive success. The principal function or purpose, then, (the “chore” says Churchland) of our cognitive faculties is not that of producing true or verisimilitudinous (nearly true) beliefs, but instead that of contributing
to survival by getting the body parts in the right place. What evolution underwrites is only (at most) that our
behavior
is reasonably adaptive to the circumstances in which our ancestors found themselves; hence it does not guarantee mostly true or verisimilitudinous beliefs. Our beliefs
might
be mostly true or verisimilitudinous (hereafter I’ll omit the “versimilitudinous”); but there is no particular reason to think they
would
be: natural selection is interested, not in truth, but in appropriate behavior. What Churchland therefore suggests is that naturalistic evolution—that is, the conjunction of metaphysical naturalism with the view that we and our cognitive faculties have arisen by way of the mechanisms and processes proposed by contemporary evolutionary theory—gives us reason to doubt two things: (a) that a
purpose
of our cognitive systems is that of serving us with true beliefs, and (b) that they
do
, in fact, furnish us with mostly true beliefs.

Indeed, Darwin himself expresses serious doubts along these lines: “With me 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?”
¹²

Nietzsche, Nagel, Stroud, Churchland, and Darwin, nontheists all, seem to concur: (naturalistic) evolution gives one a reason to doubt that human cognitive faculties produce for the most part true beliefs. Since Darwin is the standout among this group, call this thought
“Darwin’s doubt.” How shall we construe Darwin’s doubt? Can we state it a bit more exactly?

Here the idea of
conditional probability
will be useful. This is a familiar idea, one we constantly employ. The conditional probability of one proposition p on another proposition q is the probability that p is true
given that
, on the condition that, q is true.

Consider the probability that Mr. A will live to be eighty years old, given that he is now thirty-five, smokes heavily, is grossly overweight, eats only junk food, never exercises, and had grandparents all of whom died by the age of fifty: this probability is pretty low. Contrast this probability with the probability that Mr. B will live to be eighty, given that Mr. B is now seventy, has never smoked, watches his diet like a hawk, runs ten miles a day, and has grandparents all of whom lived to be over one hundred; that probability is much higher. With this notion of conditional probability in hand, we can put Darwin’s doubt as follows: the conditional probability that our cognitive faculties are reliable, given naturalism together with the proposition that we have come to be by way of evolution, is low. This is quite a mouthful: we can abbreviate it as

(1) P(R/N&E) is low.

“R” is the proposition that our cognitive faculties are reliable, “N” is naturalism, and “E” is the proposition that we and our cognitive faculties have come to be in the way proposed by the contemporary scientific theory of evolution. “P(…./___)” is shorthand for “the probability of… given ___”. (1), that is, Darwin’s doubt, is the first premise of my argument.

All of the above luminaries apparently endorse something like Darwin’s doubt; nevertheless (oddly enough) there are those who seem to disagree. In what follows, therefore, I’ll explain why Darwin’s doubt seems eminently sensible and indeed correct.

First, we must note that nearly all naturalists are also
materialists
with respect to human beings; they hold that human beings are material objects. From this perspective a human person is not (contrary to Descartes and Augustine) an immaterial substance or self that is connected with or joined to (has?) a material body. Nor is it the case that a human being is a composite that has an immaterial component; human beings do not have an immaterial soul or mind or ego. Instead, so the materialist thinks, a person
just is
her body, or perhaps some part of her body (so that talk about “my body” is misleading). I
am
my body (or maybe my brain, or its left hemisphere, or some other part of it, or some other part of my body). Nearly all naturalists would agree. They give at least three sorts of reasons for materialism. First, naturalists often argue that dualism (the thought that a human being is an immaterial self or substance intimately related to a human body) is incoherent or subject to crushing philosophical difficulties; hence, so they say, we are rationally compelled to be materialists. You can find a typical set of such objections to dualism in Daniel Dennett’s book
Consciousness Explained
.
¹³
Most of these objections (including Dennett’s) are astonishingly weak; no one not already convinced of materialism would (or at any rate should) find them at all persuasive.
¹⁴
Still, they are often trotted out as showing that we are all obliged, these enlightened days, to be materialists.

A second and somewhat better reason is this: many naturalists think it is just part of naturalism as such to have no truck with immaterial souls or selves or minds. It may not be completely easy to see or say precisely what naturalism is, but, so goes the thought, at any rate it excludes things like immaterial selves or souls. Naturalism is the idea that there is no such person as God or anything like him; immaterial selves would be too much like God, who, after all, is himself an immaterial self. This reason is really quite persuasive (for naturalists), but not wholly conclusive. That is because of the vagueness of the concept of naturalism. According to naturalism, there isn’t anything
like
God; but just how much similarity to God is tolerable, from a naturalistic perspective? After all, everything resembles God in
some
respect; how much similarity to God can a decently sensitive naturalist manage to accept? Plato’s idea of the good and Aristotle’s unmoved mover (who is also immaterial) clearly won’t pass muster, but what about immaterial soul substances? Can a proper naturalist allow such a thing? That’s not entirely easy to say. Far be it from me as an outsider, however, to intrude upon a delicate family dispute among naturalists; I hereby leave naturalists to settle this issue for themselves.

A third reason is as follows. Naturalists will ordinarily endorse Darwinian evolution; but how, they ask, could an immaterial soul or self have come to exist by way of the processes that evolutionary science posits? Thus Richard Dawkins: “Catholic Morality demands the presence of a great gulf between
Homo Sapiens
and the rest of the animal kingdom. Such a gulf is fundamentally anti-evolutionary. The sudden injection of an immortal soul in the timeline is an anti-evolutionary intrusion into the domain of science.”
¹⁵
According to contemporary evolutionary theory, new forms of life arise (for the most part) by way of natural selection working on some form of genetic variation—the
usual candidate is random genetic mutation. Though most mutations of this sort are lethal, a few are advantageous in the struggle for survival. Those lucky organisms that sport them have a reproductive advantage over those that do not, and eventually the new feature comes to dominate the population; then the process can start over. But how, they ask, could an
immaterial self or soul
evolve this way? What sort of genetic mutation would result in an immaterial soul? Could there be a section of DNA that codes, not for the production of proteins, but for an immaterial self?
¹⁶
That seems doubtful.

These reasons clearly aren’t conclusive, but most naturalists find them (or perhaps other arguments for materialism) at least reasonably compelling. For these reasons and perhaps others, most naturalists are materialists about human beings. For present purposes, therefore, I propose to assimilate materialism to naturalism; henceforth I’ll think of naturalism as including materialism, and what I’ll be arguing against is the conjunction of current evolutionary theory and naturalism, the latter including materialism.

Now what sort of thing will a belief
be
, from this materialist perspective? Suppose you are a materialist, and also think, as we ordinarily do, that there are such things as beliefs. For example, you hold the belief that Proust is more subtle than Louis L’Amour. What kind of a thing is this belief? Well, from a materialist perspective, it looks as if it would have to be something like a long-standing event or structure
in your brain or nervous system. Presumably this event will involve many neurons connected to each other in various ways. There are plenty of neurons to go around: a normal human brain contains some 100–200 billion neurons. These neurons, furthermore, are connected with other neurons via synapses; a single neuron, on the average, is connected with seven thousand of other neurons. The total number of possible brain states, then, is absolutely enormous, much greater than the number of electrons in the universe. Under certain conditions, a neuron fires—that is, produces an electrical impulse; by virtue of its connection with other neurons, this impulse can be transmitted (with appropriate modification from other neurons) down the cables of neurons that constitute effector nerves to muscles or glands, causing, for example, muscular contraction and thus behavior.

So (from the materialist’s point of view) a belief will be a neuronal event or structure of this sort, with input from other parts of the nervous system and output to still other parts as well as to muscles and glands. But if this is the sort of thing beliefs are, if they are neuronal events or structures, they will have two quite different sorts of properties. On the one hand they will have
electro-chemical
or
neuro-physiological
properties (NP properties, for short). Among these would be such properties as that of involving
n
neurons and
n*
connections between neurons, properties that specify which neurons are connected with which others, what the rates of fire in the various parts of the event are, how these rates of fire change in response to changes in input, and so on.

But if the event in question is really a
belief
, then in addition to those NP properties it will have another property as well: it will have a
content
.
¹⁷
It will be the belief that p, for some proposition p. If it’s the
belief that Proust is a more subtle writer than Louis L’Amour, then its content is the proposition
Proust is more subtle than Louis L’Amour
. My belief that naturalism is vastly overrated has as content the proposition
naturalism is vastly overrated
. (That same proposition is the content of the Chinese speaker’s belief that naturalism is vastly overrated, even though she expresses this belief by uttering a very different sentence; beliefs, unlike sentences, do not come in different languages.) It is in virtue of having content that a belief is true or false: it is true if the proposition which is its content is true, and false otherwise. My belief that all men are mortal is true because the proposition which constitutes its content is true; Hitler’s belief that the Third Reich would last a thousand years was false, because the proposition that constituted its content is (was) false.