It is time we recognized that the only thing that permits human beings to collaborate with one another in a truly open-ended way is their willingness to have their beliefs modified by new facts. Only openness to evidence and argument will secure a common world for us. Nothing guarantees that reasonable people will agree about everything, of course, but the unreasonable are certain to be divided by their dogmas. This spirit of mutual inquiry is the very antithesis of religious faith.
While we may never achieve closure in our view of the world, it seems extraordinarily likely that our descendants will look upon many of our beliefs as both impossibly quaint and suicidally stupid. Our primary task in our discourse with one another should be to identify those beliefs that seem least likely to survive another thousand years of human inquiry, or most likely to prevent it, and subject them to sustained criticism. Which of our present practices will appear most ridiculous from the point of view of those future generations that might yet survive the folly of the present? It is hard to imagine that our religious preoccupations will not top the list.26 It is natural to hope that our descendants will look upon us with gratitude. But we should also hope that they look upon us with pity and disgust, just as we view the slaveholders of our all-too-recent past. Rather than congratulate ourselves for the state of our civilization, we should consider how, in the fullness of time, we will seem hopelessly backward, and work to lay a foundation for such refinements in the present. We must find our way to a time when faith, without evidence, disgraces anyone who would claim it. Given the present state of our world, there appears to be no other future worth wanting.
It is imperative that we begin speaking plainly about the absurdity of most of our religious beliefs. 1 fear, however, that the time has not yet arrived. In this sense, what follows is written very much in the spirit of a prayer. I pray that we may one day think clearly enough about these matters to render our children incapable of killing themselves over their books. If not our children, then I suspect it could well be too late for us, because while it has never been difficult to meet your maker, in fifty years it will simply be too easy to drag everyone else along to meet him with you.27
The Nature of Belief
It is often argued that religious beliefs are somehow distinct from other claims to knowledge about the world. There is no doubt that we treat them differently-particularly in the degree to which we demand, in ordinary discourse, that people justify their beliefs-but this does not indicate that religious beliefs are special in any important sense. What do we mean when we say that a person believes a given proposition about the world? As with all questions about familiar mental events, we must be careful that the familiarity of our terms does not lead us astray. The fact that we have one word for "belief" does not guarantee that believing is itself a unitary phenomenon. An analogy can be drawn to the case of memory: while people commonly refer to their failures of "memory," decades of experiment have shown that human memory comes in many forms. Not only are our long-term and short-term memories the products of distinct and dissimilar neural circuits; they have themselves been divided into multiple subsystems.1 To speak simply of "memory," therefore, is now rather like speaking of "experience." Clearly, we must be more precise about what our mental terms mean before we attempt to understand them at the level of the brain.2
Even dogs and cats, insofar as they form associations between people, places, and events, can be said to "believe" many things about the world. But this is not the sort of believing we are after. When we talk about the beliefs to which people consciously subscribe-"The house is infested with termites," "Tofu is not a dessert," "Muhammad ascended to heaven on a winged horse"-we are talking about beliefs that are communicated, and acquired, linguistically. Believing a given proposition is a matter of believing that it faithfully represents some state of the world, and this fact yields some immediate insights into the standards by which our beliefs should function.3 In particular, it reveals why we cannot help but value evidence and demand that propositions about the world logically cohere. These constraints apply equally to matters of religion. "Freedom of belief" (in anything but the legal sense) is a myth. We will see that we are no more free to believe whatever we want about God than we are free to adopt unjustified beliefs about science or history, or free to mean whatever we want when using words like "poison" or "north" or "zero." Anyone who would lay claim to such entitlements should not be surprised when the rest of us stop listening to him.
Beliefs as Principles of Action
The human brain is a prolific generator of beliefs about the world. In fact, the very humanness of any brain consists largely in its capacity to evaluate new statements of propositional truth in light of innumerable others that it already accepts. By recourse to intuitions of truth and falsity, logical necessity and contradiction, human beings are able to knit together private visions of the world that largely cohere. What neural events underlie this process? What must a brain do in order to believe that a given statement is true or false We currently have no idea. Language processing must play a large role, of course, but the challenge will be to discover how the brain brings the products of perception, memory, and reasoning to bear on individual propositions and magically transforms them into the very substance of our living.
It was probably the capacity for movement, enjoyed by certain primitive organisms, that drove the evolution of our sensory and cognitive faculties. This follows from the fact that if no creature could do anything with the information it acquired from the world, nature could not have selected for improvements in the physical structures that gather, store, and process such information. Even a sense as primitive as vision, therefore, seems predicated on the existence of a motor system. If you cannot catch food, avoid becoming food yourself, or wander off a cliff, there does not seem to be much reason to see the world in the first place-and certainly refinements in vision, of the sort found everywhere in the animal kingdom, would never have come about at all.
For this reason, it seems uncontroversial to say that all higher-order cognitive states (of which beliefs are an example) are in some way an outgrowth of our capacity for action. In adaptive terms, belief has been extraordinarily useful. It is, after all, by believing various propositions about the world that we predict events and consider the likely consequences of our actions. Beliefs are principles of action: whatever they may be at the level of the brain, they are processes by which our understanding (and misunderstanding) of the world is represented and made available to guide our behavior.4
The power that belief has over our emotional lives appears to be total. For every emotion that you are capable of feeling, there is surely a belief that could invoke it in a matter of moments. Consider the following proposition:
Your daughter is being slowly tortured in an English jail.
What is it that stands between you and the absolute panic that such a proposition would loose in the mind and body of a person who believed it? Perhaps you do not have a daughter, or you know her to be safely at home, or you believe that English jailors are renowned for their congeniality. Whatever the reason, the door to belief has not yet swung upon its hinges.
The link between belief and behavior raises the stakes considerably. Some propositions are so dangerous that it may even be ethical to kill people for believing them. This may seem an extraordinary claim, but it merely enunciates an ordinary fact about the world in which we live. Certain beliefs place their adherents beyond the reach of every peaceful means of persuasion, while inspiring them to commit acts of extraordinary violence against others. There is, in fact, no talking to some people. If they cannot be captured, and they often cannot, otherwise tolerant people may be justified in killing them in self-defense. This is what the United States attempted in Afghanistan, and it is what we and other Western powers are bound to attempt, at an even greater cost to ourselves and to innocents abroad, elsewhere in the Muslim world. We will continue to spill blood in what is, at bottom, a war of ideas.5
The N
ecessity for Logical Coherence
The first thing to notice about beliefs is that they must suffer the company of their neighbors. Beliefs are both logically and semantically related. Each constrains, and is in turn constrained by, many others. A belief like the Boeing 747 is the world's best airplane logically entails many other beliefs that are both more basic (e.g., airplanes exist) and more derivative (e.g., 747s are better than 757s). The belief that some men are husbands demands that the proposition some women are wives also be endorsed, because the very terms "husband" and "wife" mutually define one another.6 In fact, logical and semantic constraints appear to be two sides of the same coin, because our need to understand what words mean in each new context requires that our beliefs be free from contradiction (at least locally). If I am to mean the same thing by the word "mother" from one instance to the next, I cannot both believe my mother was born in Rome and believe my mother was born in Nevada. Even if my mother were born on an airplane flying at supersonic speeds, these propositions cannot both be true. There are tricks to be played here-perhaps there is a town called "Rome" somewhere in the state of Nevada; or perhaps "mother" means "biological mother" in one sentence and "adoptive mother" in another-but these exceptions only prove the rule. To know what a given belief is about, I must know what my words mean; to know what my words mean, my beliefs must be generally consistent.7 There is just no escaping the fact that there is a tight relationship between the words we use, the type of thoughts we can think, and what we can believe to be true about the world.
And behavioral constraints are just as pressing. When going to a friend's home for dinner, I cannot both believe that he lives north of Main Street and south of Main Street and then act on the basis of what I believe. A normal degree of psychological and bodily integration precludes my being motivated to head in two opposing directions at once.
Personal identity itself requires such consistency: unless a person's beliefs are highly coherent, he will have as many identities as there are mutually incompatible sets of beliefs careening around his brain. If you doubt this, just try to imagine the subjectivity of a man who believes that he spent the entire day in bed with the flu, but also played a round of golf; that his name is Jim, and that his name is Tom; that he has a young son, and that he is childless. Multiply these incompatible beliefs indefinitely, and any sense that their owner is a single subject entirely disappears. There is a degree of logical inconsistency that is incompatible with our notion of personhood.
So it seems that the value we put on logical consistency is neither misplaced nor mysterious. In order for my speech to be intelligible to others-and, indeed, to myself -my beliefs about the world must largely cohere. In order for my behavior to be informed by what I believe, I must believe things that admit of behavior that is, at a minimum, possible. Certain logical relations, after all, seem etched into the very structure of our world.8 The telephone rings ... either it is my brother on the line, or it isn't. I may believe one proposition or the other-or I may believe that I do not know-but under no circumstances is it acceptable for me to believe both.
Departures from normativity, in particular with respect to the rules of inference that lead us to construct new beliefs on the basis of old ones, have been the subject of much research and much debate.9 Whatever construal of these matters one adopts, no one believes that human beings are perfect engines of coherence. Our inevitable failures of rationality can take many forms, ranging from mere logical inconsistencies to radical discontinuities in subjectivity itself. Most of the literature on "self-deception," for instance, suggests that a person can tacitly believe one proposition, while successfully convincing himself of its antithesis (e.g., my wife is having an affair; my wife is faithful), though considerable controversy still surrounds the question of how (or whether) such cognitive contortions actually occur.10 Other failures of psychological integration-ranging from "split-brain" patients to cases of "multiple-personality "-are at least partially explicable in terms of areas of belief processing in the brain that have become structurally and/or functionally partitioned from one another.
The American Embassy
A case in point: While traveling in France, my fiancée and I experienced a bizarre partitioning of our beliefs about the American embassy in Paris:
Belief system 1: As the events of September 11 still cast a shadow over the world, we had decided to avoid obvious terrorist targets while traveling. First on our list of such places was the American embassy in Paris. Paris is home to the largest Muslim population in the Western world, and this embassy had already been the target of a foiled suicide plot. The American embassy would have been the last place we would have willingly visited while in France.
Belief system 2: Prior to our arrival in Paris, we had great difficulty finding a hotel room. Every hotel we checked was full, except for one on the Right Bank, which had abundant vacancies. The woman at reservations even offered us a complimentary upgrade to a suite. She also gave us a choice of views-we could face the inner courtyard, or outward, overlooking the American embassy. "Which view would you choose?" I asked. "The view of the embassy," she replied. "It's much more peaceful." I envisioned a large, embassy garden. "Great," I said. "We'll take it."
The next day, we arrived at the hotel and found that we had been given a room with a courtyard view. Both my fiancée and I were disappointed. We had, after all, been promised a view of the American embassy.
We called a friend living in Paris to inform her of our whereabouts. Our friend, who is wise in the ways of the world, had this to say: "That hotel is directly next to the American embassy. That's why they're offering you an upgrade. Have you guys lost your minds? Do you know what day it is? It's the Fourth of July."
The appearance of this degree of inconsistency in our lives was astounding. We had spent the better part of the day simultaneously trying to avoid and gain proximity to the very same point in space. Realizing this, we could scarcely have been more surprised had we both grown antlers.
But what seems psychologically so mysterious may be quite trivial in neurological terms. It appears that the phrase "American embassy," spoken in two different contexts, merely activated distinct networks of association within our brains. Consequently, the phrase had acquired two distinct meanings. In the first case, it signified a prime terrorist target; in the second, it promised a desirable view from a hotel window. The significance of the phrase in the world, however, is single and indivisible, since only one building answers to this name in Paris. The communication between these networks of neurons appeared to be negligible; our brains were effectively partitioned. The flimsiness of this partition was revealed by just how easily it came down. All it took for me to unify my fiancée's outlook on this subject was to turn to her-she who was still silently coveting a view of the American embassy-and say, with obvious alarm, "This hotel is ten feet from the American embassy!" The partition came down, and she was as flabbergasted as I was.
And yet, the psychologically irreconcilable facts are these: on the day in question, never was there a time when we would have willingly placed ourselves near the American embassy, and never was there a time when we were not eager to move to a room with a view of it.
While behavioral and linguistic necessity demands that we seek coherence among our beliefs wherever we can, we know that total coherence, even in a maximally integrated brain, would be impossible to achieve. This becomes apparent the moment we imagine a person's beliefs recorded as a list of assertions like I am walking in the park; Parks generally have animals; Lions are animals; and so on-each being a belief unto itself, as well as a possible basis upon which to form further inferences (both good ones: I may soon see an animal; and bad ones: I may soon see a lion), and hence new beliefs, about the world. If perfect coherence is to be had, each new belief must be checked against all others, and every combination thereof, for logical contradictions.11 But here we encounter a minor computational difficulty: the number of necessary comparisons grows exponentially as ea
ch new proposition is added to the list. How many beliefs could a perfect brain check for logical contradictions? The answer is surprising. Even if a computer were as large as the known universe, built of components no larger than protons, with switching speeds as fast as the speed of light, all laboring in parallel from the moment of the big bang up to the present, it would still be fighting to add a 300th belief to its list.12 What does this say about the possibility of our ever guaranteeing that our worldview is perfectly free from contradiction? It is not even a dream within a dream.13 And yet, given the demands of language and behavior, it remains true that we must strive for coherence wherever it is in doubt, because failure here is synonymous with a failure either of linguistic sense or of behavioral possibility.14
Beliefs as Representations of the World
For even the most basic knowledge of the world to be possible, regularities in a nervous system must consistently mirror regularities in the environment. If a different assemblage of neurons in my brain fired whenever I saw a person's face, I would have no way to form a memory of him. His face could look like a face one moment and a toaster the next, and I would have no reason to be surprised by the inconsistency, for there would be nothing for a given pattern of neural activation to be consistent with. As Stephen Pinker points out, it is only the orderly mirroring between a system that processes information (a brain or a computer) and the laws of logic or probability that explains "how rationality can emerge from mindless physical process" in the first place.15 Words are arranged in a systematic and rule-based way (syntax), and beliefs are likewise (in that they must logically cohere), because both body and world are so arranged. Consider the statement There is an apple and an orange in Jack's lunch box. The syntactical (and hence logical) significance of the word "and" guarantees that anyone who believes this statement will also believe the following propositions: There is an apple in Jack's lunch box and There is an orange in Jack's lunch box. This is not due to some magical property that syntax holds over the world; rather, it is a simple consequence of the fact that we use words like "and" to mirror the orderly behavior of objects. Someone who will endorse the conjunction of two statements, while denying them individually, either does not understand the use of the word "and" or does not understand things like apples, oranges, and lunch boxes.16 It just so happens that we live in a universe in which, if you put an apple and an orange in Jack's lunch box, you will be able to pull out an apple, an orange, or both. There is a point at which the meanings of words, their syntactical relations, and rationality itself can no longer be divorced from the orderly behavior of objects in the world.17