True Believers:
The Intentional Strategy
and Why It Works
Daniel C. Dennett
1981
DEATH SPEAKS: There was a merchant in Baghdad who sent his servant to market to buy provisions and in a little
while the servant came back, white and trembling, and said: "Master, just now when I was in the market-place I was
jostled by a woman in the crowd and when I turned I saw it was Death that jostled me. She looked at me and made a
threatening gesture; now, lend me your horse, and I will ride away from this city and avoid my fate. I will go to
Samarra and there Death will not find me." The merchant lent him his horse, and the servant mounted it, and he dug
his spurs in its flanks and as fast as the horse could gallop he went. Then the merchant went down to the market-place
and he saw me standing in the crowd, and he came to me and said: "Why did you make a threatening gesture to my
servant when you saw him this morning?" "That was not a threatening gesture," I said, "it was only a start of
surprise. I was astonished to see him in Baghdad, for I had an appointment with him tonight in Samarra.''
W. Somerset Maugham
In the social sciences, talk about belief is ubiquitous. Since social scientists are typically self-conscious
about their methods, there is also a lot of talk about talk about belief And since belief is a genuinely
curious and perplexing phenomenon, showing many different faces to the world, there is abundant
controversy. Sometimes belief attribution appears to be a dark, risky, and imponderable
businessespecially when exotic, and more particularly religious or superstitious, beliefs are in the
limelight. These are not the only troublesome cases; we also court argument and skepticism when we
attribute beliefs to nonhuman animals, or to infants, or to computers or robots. Or when the beliefs we
feel constrained to attribute to an apparently healthy adult
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member of our own society are contradictory, or even just wildly false. A biologist colleague of mine
was once called on the telephone by a man in a bar who wanted him to settle a bet. The man asked: "Are
rabbits birds?" "No" said the biologist. "Damn!" said the man as he hung up. Now could he really have
believed that rabbits were birds? Could anyone really and truly be attributed that belief? Perhaps, but it
would take a bit of a story to bring us to accept it.
In all of these cases, belief attribution appears beset with subjectivity, infected with cultural relativism,
prone to "indeterminacy of radical translation"clearly an enterprise demanding special talents: the art
of phenomenological analysis, hermeneutics, empathy, Verstehen, and all that. On other occasions,
normal occasions, when familiar beliefs are the topic, belief attribution looks as easy as speaking prose
and as objective and reliable as counting beans in a dish. Particularly when these straightforward cases
are before us, it is quite plausible to suppose that in principle (if not yet in practice) it would be possible
to confirm these simple, objective belief attributions by finding something inside the believer's headby
finding the beliefs themselves, in effect. "Look", someone might say, "either you believe there's milk in
the fridge or you don't believe there's milk in the fridge" (you might have no opinion, in the latter case).
But if you do believe this, that's a perfectly objective fact about you, and it must come down in the end
to your brain's being in some particular physical state. If we knew more about physiological psychology,
we could in principle determine the facts about your brain state and thereby determine whether or not
you believe there is milk in the fridge, even if you were determined to be silent or disingenuous on the
topic. In principle, on this view, physiological psychology could trump the resultsor nonresultsof
any "black box" method in the social sciences that divines beliefs (and other mental features) by
behavioral, cultural, social, historical, external criteria.
These differing reflections congeal into two opposing views on the nature of belief attribution, and
hence on the nature of belief. The latter, a variety of realism, likens the question of whether a person has
a particular belief to the question of whether a person is infected with a particular virusa perfectly
objective internal matter of fact about which an observer can often make educated guesses of great
reliability. The former, which we could call interpretationism if we absolutely had to give it a name,
likens the question of whether a person has a particular belief to the question of whether a person is
immoral, or has style,
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or talent, or would make a good wife. Faced with such questions, we preface our answers with "well, it
all depends on what you're interested in", or make some similar acknowledgment of the relativity of the
issue. "It's a matter of interpretation", we say. These two opposing views, so baldly stated, do not fairly
represent any serious theorists' positions, but they do express views that are typically seen as mutually
exclusive and exhaustive; the theorist must be friendly with one and only one of these themes.
I think this is a mistake. My thesis will be that while belief is a perfectly objective phenomenon (that
apparently makes me a realist), it can be discerned only from the point of view of one who adopts a
certain predictive strategy, and its existence can be confirmed only by an assessment of the success of
that strategy (that apparently makes me an interpretationist).
First I will describe the strategy, which I call the intentional strategy or adopting the intentional stance.
To a first approximation, the intentional strategy consists of treating the object whose behavior you want
to predict as a rational agent with beliefs and desires and other mental states exhibiting what Brentano
and others call intentionality. The strategy has often been described before, but I shall try to put this very
familiar material in a new light by showing how it works and by showing how well it works.
Then I will argue that any objector as I shall say, any systemwhose behavior is well predicted by
this strategy is in the fullest sense of the word a believer. What it is to be a true believer is to be an
intentional system, a system whose behavior is reliably and voluminously predictable via the intentional
strategy. I have argued for this position before (1971/78, 1976/78, 1978a), and my arguments have so far
garnered few converts and many presumed counterexamples. I shall try again here, harder, and shall also
deal with several compelling objections.
1 The intentional strategy and how it works
There are many strategies, some good, some bad. Here is a strategy, for instance, for predicting the
future behavior of a person: determine the date and hour of the person's birth and then feed this modest
datum into one or another astrological algorithm for generating predictions of the person's prospects.
This strategy is deplorably popular. Its popularity is deplorable only because we have such good reasons
for believing
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that it does not work (pace Feyerabend 1978). When astrological predictions come true this is sheer
luck, or the result of such vagueness or ambiguity in the prophecy that almost any eventuality can be
construed to confirm it. But suppose the astrological strategy did in fact work well on some people. We
could call those people astrological systemssystems whose behavior was, as a matter of fact,
predictable by the astrological strategy. If there were such people, such astrological systems, we would
be more interested than most of us in fact are in how the astrological strategy worksthat is, we would
be interested in the rules, principles, or methods of astrology. We could find out how the strategy works
by asking astrologers, reading their books, and observing them in action. But we would also be curious
about why it worked. We might find that astrologers had no useful opinions about this latter
questionthey either had no theory of why it worked or their theories were pure hokum. Having a good
strategy is one thing; knowing why it works is another.
So far as we know, however, the class of astrological systems is empty; so the astrological strategy is of
interest only as a social curiosity. Other strategies have better credentials. Consider the physical strategy,
or physical stance; if you want to predict the behavior of a system, determine its physical constitution
(perhaps all the way down to the microphysical level) and the physical nature of the impingements upon
it, and use your knowledge of the laws of physics to predict the outcome for any input. This is the grand
and impractical strategy of Laplace for predicting the entire future of everything in the universe; but it
has more modest, local, actually usable versions. The chemist or physicist in the laboratory can use this
strategy to predict the behavior of exotic materials, but equally the cook in the kitchen can predict the
effect of leaving the pot on the burner too long. The strategy is not always practically available, but that
it will always work in principle is a dogma of the physical sciences. (I ignore the minor complications
raised by the subatomic indeterminacies of quantum physics.)
Sometimes, in any event, it is more effective to switch from the physical stance to what I call the design
stance, where one ignores the actual (possibly messy) details of the physical constitution of an object,
and, on the assumption that it has a certain design, predicts that it will behave as it is designed to behave
under various circumstances. For instance, most users of computers have not the foggiest idea what
physical principles are responsible for the computer's highly reliable, and hence predictable, behavior.
But if they have a good idea of what
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the computer is designed to do (a description of its operation at any one of the many possible levels of
abstraction), they can predict its behavior with great accuracy and reliability, subject to disconfirmation
only in the cases of physical malfunction. Less dramatically, almost anyone can predict when an alarm
clock will sound on the basis of the most casual inspection of its exterior. One does not know or care to
know whether it is spring wound, battery driven, sunlight powered, made of brass wheels and jewel
bearings or silicon chipsone just assumes that it is designed so that the alarm will sound when it is set
to sound, and it is set to sound where it appears to be set to sound, and the clock will keep on running
until that time and beyond, and is designed to run more or less accurately, and so forth. For more
accurate and detailed design stance predictions of the alarm clock, one must descend to a less abstract
level of description of its design; for instance, to the level at which gears are described, but their material
is not specified.
Only the designed behavior of a system is predictable from the design stance, of course. If you want to
predict the behavior of an alarm clock when it is pumped full of liquid helium, revert to the physical
stance. Not just artifacts but also many biological objects (plants and animals, kidneys and hearts,
stamens and pistils) behave in ways that can be predicted from the design stance. They are not just
physical systems but designed systems.
Sometimes even the design stance is practically inaccessible, and then there is yet another stance or
strategy one can adopt: the intentional stance. Here is how it works: first you decide to treat the object
whose behavior is to be predicted as a rational agent; then you figure out what beliefs that agent ought to
have, given its place in the world and its purpose. Then you figure out what desires it ought to have, on
the same considerations, and finally you predict that this rational agent will act to further its goals in the
light of its beliefs. A little practical reasoning from the chosen set of beliefs and desires will in
manybut not allinstances yield a decision about what the agent ought to do; that is what you predict
the agent will do.
The strategy becomes clearer with a little elaboration. Consider first how we go about populating each
other's heads with beliefs. A few truisms: sheltered people tend to be ignorant; if you expose someone to
something he comes to know all about it. In general, it seems, we come to believe all the truths about the
parts of the world around us we are put in a position to learn about. Exposure to xthat is, sensory
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confrontation with x over some suitable period of timeis the normally sufficient condition for knowing
(or having true beliefs) about x. As we say, we come to know all about the things around us. Such
exposure is only normally sufficient for knowledge, but this is not the large escape hatch it might
appear; our threshold for accepting abnormal ignorance in the face of exposure is quite high. "I didn't
know the gun was loaded", said by one who was observed to be present, sighted, and awake during the
loading, meets with a variety of utter skepticism that only the most outlandish supporting tale could
overwhelm.
Of course we do not come to learn or remember all the truths our sensory histories avail us. In spite of
the phrase "know all about", what we come to know, normally, are only all the relevant truths our
sensory histories avail us. I do not typically come to know the ratio of spectacle-wearing people to
trousered people in a room I inhabit, though if this interested me, it would be readily learnable. It is not
just that some facts about my environment are below my thresholds of discrimination or beyond the
integration and holding power of my memory (such as the height in inches of all the people present), but
that many perfectly detectable, graspable, memorable facts are of no interest to me and hence do not
come to be believed by me. So one rule for attributing beliefs in the intentional strategy is this: attribute
as beliefs all the truths relevant to the system's interests (or desires) that the system's experience to date
has made available. This rule leads to attributing somewhat too muchsince we all are somewhat
forgetful, even of important things. It also fails to capture the false beliefs we are all known to have. But
the attribution of false belief, any false belief, requires a special genealogy, which will be seen to consist
in the main in true beliefs. Two paradigm cases: S believes (falsely) that p, because S believes (truly)
that Jones told him that p, that Jones is pretty clever, that Jones did not intend to deceive him, ... and so
on. Second case: S believes (falsely) that there is a snake on the barstool, because S believes (truly) that
he seems to see a snake on the barstool, is himself sitting in a bar not a yard from the barstool he sees,
and so forth. The falsehood has to start somewhere: the seed may be sown in hallucination, illusion, a
normal variety of simple misperception, memory deterioration, or deliberate fraud, for instance; but the
false beliefs that are reaped grow in a culture medium of true beliefs.
Then there are the arcane and sophisticated beliefs, true and false, that are so often at the focus of
attention in discussions of belief attribution. They do not arise directly, goodness knows, from exposure
to
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mundane things and events, but their attribution requires tracing out a lineage of mainly good argument
or reasoning from the bulk of beliefs already attributed. An implication of the intentional strategy, then,
is that true believers mainly believe truths. If anyone could devise an agreed-upon method of
individuating and counting beliefs (which I doubt very much), we would see that all but the smallest
portion (say, less than ten percent) of a person's beliefs were attributable under our first rule.1
Note that this rule is a derived rule, an elaboration and further specification of the fundamental rule:
attribute those beliefs the system ought to have. Note also that the rule interacts with the attribution of
desires. How do we attribute the desires (preferences, goals, interests) on whose basis we will shape the
list of beliefs? We attribute the desires the system ought to have. That is the fundamental rule. It
dictates, on a first pass, that we attribute the familiar list of highest, or most basic, desires to people:
survival, absence of pain, food, comfort, procreation, entertainment. Citing any one of these desires
typically terminates the "Why?" game of reason giving. One is not supposed to need an ulterior motive
for desiring comfort or pleasure or the prolongation of one's existence. Derived rules of desire
attribution interact with belief attributions. Trivially, we have the rule: attribute desires for those things a
system believes to be good for it. Somewhat more informatively, attribute desires for those things a
system believes to be best means to other ends it desires. The attribution of bizarre and detrimental
desires thus requires, like the attribution of false beliefs, special stories.
The interaction between belief and desire becomes trickier when we consider what desires we attribute
on the basis of verbal behavior. The capacity to express desires in language opens the floodgates of
desire attribution. "I want a two-egg mushroom omelet, some French bread and butter, and a half bottle
of lightly chilled white Burgundy." How could one begin to attribute a desire for anything so specific in
the absence of such verbal declaration? How, indeed, could a creature come to contract such a specific
desire without the aid of language? Language enables us to formulate highly specific desires, but it also
forces us on occasion to commit ourselves to desires altogether more stringent in their conditions of
satisfaction than anything we would otherwise have any reason to endeavor to satisfy. Since in order to
get what you want you often have to say what you want, and since you often cannot say what you want
without saying something more
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specific than you antecedently mean, you often end up giving others evidence (the very best of evidence,
your unextorted word) that you desire things or states of affairs far more particular than would satisfy
youor better, than would have satisfied you, for once you have declared, being a man of your word,
you acquire an interest in satisfying exactly the desire you declared and no other.
"I'd like some baked beans, please."
"Yes sir. How many?"
You might well object to having such a specification of desire demanded of you, but in fact we are all
socialized to accede to similar requirements in daily lifeto the point of not noticing it, and certainly
not feeling oppressed by it. I dwell on this because it has a parallel in the realm of belief, where our
linguistic environment is forever forcing us to giveor concedeprecise verbal expression to
convictions that lack the hard edges verbalization endows them with (see Dennett 1969, pp. 184-85,
1978a). By concentrating on the results of this social force, while ignoring its distorting effect, one can
easily be misled into thinking that it is obvious that beliefs and desires are rather like sentences stored in
the head. Being language-using creatures, it is inevitable that we should often come to believe that some
particular, actually formulated, spelled, and punctuated sentence is true, and that on other occasions we
should come to want such a sentence to come true; but these are special cases of belief and desire and as
such may not be reliable models for the whole domain.
That is enough, on this occasion, about the principles of belief and desire attribution to be found in the
intentional strategy. What about the rationality one attributes to an intentional system? One starts with
the ideal of perfect rationality and revises downward as circumstances dictate. That is, one starts with
the assumption that people believe all the implications of their beliefs and believe no contradictory pairs
of beliefs. This does not create a practical problem of clutter (infinitely many implications, for instance),
for one is interested only in ensuring that the system one is predicting is rational enough to get to the
particular implications that are relevant to its behavioral predicament of the moment. Instances of
irrationality, or of finitely powerful capacities of inferences, raise particularly knotty problems of
interpretation, which I will set aside on this occasion (see Dennett 1981/87b and Cherniak 1986).
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For I want to turn from the description of the strategy to the question of its use. Do people actually use
this strategy? Yes, all the time. There may someday be other strategies for attributing belief and desire
and for predicting behavior, but this is the only one we all know now. And when does it work? It works
with people almost all the time. Why would it not be a good idea to allow individual Oxford colleges to
create and grant academic degrees whenever they saw fit? The answer is a long story, but very easy to
generate. And there would be widespread agreement about the major points. We have no difficulty
thinking of the reasons people would then have for acting in such ways as to give others reasons for
acting in such ways as to give others reasons for ... creating a circumstance we would not want. Our use
of the intentional strategy is so habitual and effortless that the role it plays in shaping our expectations
about people is easily overlooked. The strategy also works on most other mammals most of the time. For
instance, you can use it to design better traps to catch those mammals, by reasoning about what the
creature knows or believes about various things, what it prefers, what it wants to avoid. The strategy
works on birds, and on fish, and on reptiles, and on insects and spiders, and even on such lowly and
unenterprising creatures as clams (once a clam believes there is danger about, it will not relax its grip on
its closed shell until it is convinced that the danger has passed). It also works on some artifacts: the chess-
playing computer will not take your knight because it knows that there is a line of ensuing play that
would lead to losing its rook, and it does not want that to happen. More modestly, the thermostat will
turn off the boiler as soon as it comes to believe the room has reached the desired temperature.
The strategy even works for plants. In a locale with late spring storms, you should plant apple varieties
that are particularly cautious about concluding that it is springwhich is when they want to blossom, of
course. It even works for such inanimate and apparently undesigned phenomena as lightning. An
electrician once explained to me how he worked out how to protect my underground water pump from
lightning damage: lightning, he said, always wants to find the best way to ground, but sometimes it gets
tricked into taking second-best paths. You can protect the pump by making another, better path more
obvious to the lightning.
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2 True believers as intentional systems
Now clearly this is a motley assortment of "serious" belief attributions, dubious belief attributions,
pedagogically useful metaphors, faons de parler, and, perhaps worse, outright frauds. The next task
would seem to be distinguishing those intentional systems that really have beliefs and desires from those
we may find it handy to treat as if they had beliefs and desires. But that would be a Sisyphean labor, or
else would be terminated by fiat. A better understanding of the phenomenon of belief begins with the
observation that even in the worst of these cases, even when we are surest that the strategy works for the
wrong reasons, it is nevertheless true that it does work, at least a little bit. This is an interesting fact,
which distinguishes this class of objects, the class of intentional systems, from the class of objects for
which the strategy never works. But is this so? Does our definition of an intentional system exclude any
objects at all? For instance, it seems the lectern in this lecture room can be construed as an intentional
system, fully rational, believing that it is currently located at the center of the civilized world (as some of
you may also think), and desiring above all else to remain at that center. What should such a rational
agent so equipped with belief and desire do? Stay put, clearlywhich is just what the lectern does. I
predict the lectern's behavior, accurately, from the intentional stance, so is it an intentional system? If it
is, anything at all is.
What should disqualify the lectern? For one thing, the strategy does not recommend itself in this case,
for we get no predictive power from it that we did not antecedently have. We already knew what the
lectern was going to donamely nothingand tailored the beliefs and desires to fit in a quite
unprincipled way. In the case of people or animals or computers, however, the situation is different. In
these cases often the only strategy that is at all practical is the intentional strategy; it gives us predictive
power we can get by no other method. But, it will be urged, this is no difference in nature, but merely a
difference that reflects upon our limited capacities as scientists. The Laplacean omniscient physicist
could predict the behavior of a computeror of a live human body, assuming it to be ultimately
governed by the laws of physicswithout any need for the risky, short-cut methods of either the design
or intentional strategies. For people of limited mechanical aptitude, the intentional interpretation of a
simple thermostat is a handy and largely innocuous crutch, but the engineers among us can quite fully
grasp its internal operation without the aid of this
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anthropomorphizing. It may be true that the cleverest engineers find it practically impossible to maintain
a clear conception of more complex systems, such as a time-sharing computer system or remote-
controlled space probe, without lapsing into an intentional stance (and viewing these devices as asking
and telling, trying and avoiding, wanting and believing), but this is just a more advanced case of human
epistemic frailty. We would not want to classify these artifacts with the true believersourselveson
such variable and parochial grounds, would we? Would it not be intolerable to hold that some artifact or
creature or person was a believer from the point of view of one observer, but not a believer at all from
the point of view of another, cleverer observer? That would be a particularly radical version of
interpretationism, and some have thought I espoused it in urging that belief be viewed in terms of the
success of the intentional strategy. I must confess that my presentation of the view has sometimes
invited that reading, but I now want to discourage it. The decision to adopt the intentional stance is free,
but the facts about the success or failure of the stance, were one to adopt it, are perfectly objective.
Once the intentional strategy is in place, it is an extraordinarily powerful tool in predictiona fact that
is largely concealed by our typical concentration on the cases in which it yields dubious or unreliable
results. Consider, for instance, predicting moves in a chess game. What makes chess an interesting
game, one can see, is the unpredictability of one's opponent's moves, except in those cases where moves
are ''forced"where there is clearly one best movetypically the least of the available evils. But this
unpredictability is put in context when one recognizes that in the typical chess situation there are very
many perfectly legal and hence available moves, but only a fewperhaps half a dozenwith anything
to be said for them, and hence only a few high-probability moves according to the intentional strategy.
Even when the intentional strategy fails to distinguish a single move with a highest probability, it can
dramatically reduce the number of live options.
The same feature of the intentional strategy is apparent when it is applied to "real world" cases. It is
notoriously unable to predict the exact purchase and sell decisions of stock traders, for instance, or the
exact sequence of words a politician will utter when making a scheduled speech. But one's confidence
can be very high indeed about slightly less specific predictions: that the particular trader will not buy
utilities today, or that the politician will side with the unions against his
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party, for example. This inability to predict fine-grained descriptions of actions, looked at another way,
is a source of strength for the intentional strategy, for it is this neutrality with regard to details of
implementation that permits one to exploit the intentional strategy in complex cases, for instance, in
chaining predictions (see Dennett 1978). Suppose the US secretary of State were to announce he was a
paid agent of the KGB. What an unparalleled event! How unpredictable its consequences! Yet in fact we
can predict dozens of not terribly interesting but perfectly salient consequences, and consequences of
consequences. The President would confer with the rest of the Cabinet, which would support his
decision to relieve the Secretary of State of his duties pending the results of various investigations,
psychiatric and political, and all this would be reported at a news conference to people who would write
stories that would be commented upon in editorials that would be read by people who would write
letters to the editors, and so forth. None of that is daring prognostication, but note that it describes an arc
of causation in space-time that could not be predicted under any description by any imaginable practical
extension of physics or biology.
The power of the intentional strategy can be seen even more sharply with the aid of an objection first
raised by Robert Nozick some years ago. Suppose, he suggested, some beings of vastly superior
intelligencefrom Mars, let us saywere to descend upon us, and suppose that we were to them as
simple thermostats are to clever engineers. Suppose, that is, that they did not need the intentional
stanceor even the design stanceto predict our behavior in all its detail. They can be supposed to be
Laplacean super-physicists, capable of comprehending the activity on Wall Street, for instance, at the
microphysical level. Where we see brokers and buildings and sell orders and bids, they see vast
congeries of subatomic particles milling aboutand they are such good physicists that they can predict
days in advance what ink marks will appear each day on the paper tape labeled "Closing Dow Jones
Industrial Average". They can predict the individual behaviors of all the various moving bodies they
observe without ever treating any of them as intentional systems. Would we be right then to say that
from their point of view we really were not believers at all (any more than a simple thermostat is)? If so,
then our status as believers is nothing objective, but rather something in the eye of the
beholderprovided the beholder shares our intellectual limitations.
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Our imagined Martians might be able to predict the future of the human race by Laplacean methods, but
if they did not also see us as intentional systems, they would be missing something perfectly objective:
the patterns in human behavior that are describable from the intentional stance, and only from that
stance, and that support generalizations and predictions. Take a particular instance in which the Martians
observe a stockbroker deciding to place an order for 500 shares of General Motors. They predict the
exact motions of his fingers as he dials the phone and the exact vibrations of his vocal cords as he
intones his order. But if the Martians do not see that indefinitely many different patterns of finger
motions and vocal cord vibrationseven the motions of indefinitely many different individualscould
have been substituted for the actual particulars without perturbing the subsequent operation of the
market, then they have failed to see a real pattern in the world they are observing. Just as there are
indefinitely many ways of being a spark plugand one has not understood what an internal combustion
engine is unless one realizes that a variety of different devices can be screwed into these sockets without
affecting the performance of the engineso there are indefinitely many ways of ordering 500 shares of
General Motors, and there are societal sockets in which one of these ways will produce just about the
same effect as any other. There are also societal pivot points, as it were, where which way people go
depends on whether they believe that p, or desire A, and does not depend on any of the other infinitely
many ways they may be alike or different.
Suppose, pursuing our Martian fantasy a little further, that one of the Martians were to engage in a
predicting contest with an Earthling. The Earthling and the Martian observe (and observe each other
observing) a particular bit of local physical transaction. From the Earthling's point of view, this is what
is observed. The telephone rings in Mrs. Gardner's kitchen. She answers, and this is what she says: "Oh,
hello dear. You're coming home early? Within the hour? And bringing the boss to dinner? Pick up a
bottle of wine on the way home then, and drive carefully." On the basis of this observation, our
Earthling predicts that a large metallic vehicle with rubber tires will come to a stop on the drive within
one hour, disgorging two human beings, one of whom will be holding a paper bag containing a bottle
containing an alcoholic fluid. The prediction is a bit risky, perhaps, but a good bet on all counts. The
Martian makes the same prediction, but has to avail himself of much more information about an
extraordinary number of
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interactions of which, so far as he can tell, the Earthling is entirely ignorant. For instance, the
deceleration of the vehicle at intersection A, five miles from the house, without which there would have
been a collision with another vehiclewhose collision course had been laboriously calculated over
some hundreds of meters by the Martian. The Earthling's performance would look like magic! How did
the Earthling know that the human being who got out of the car and got the bottle in the shop would get
back in? The coming true of the Earthling's prediction, after all the vagaries, intersections, and branches
in the paths charted by the Martian, would seem to anyone bereft of the intentional strategy as marvelous
and inexplicable as the fatalistic inevitability of the appointment in Samarra. Fatalistsfor instance,
astrologersbelieve that there is a pattern in human affairs that is inexorable, that will impose itself
come what may, that is, no matter how the victims scheme and second-guess, no matter how they twist
and turn in their chains. These fatalists are wrong, but they are almost right. There are patterns in human
affairs that impose themselves, not quite inexorably but with great vigor, absorbing physical
perturbations and variations that might as well be considered random; these are the patterns that we
characterize in terms of the beliefs, desires, and intentions of rational agents.
No doubt you will have noticed, and been distracted by, a serious flaw in our thought experiment: the
Martian is presumed to treat his Earthling opponent as an intelligent being like himself, with whom
communication is possible, a being with whom one can make a wager, against whom one can compete.
In short, a being with beliefs (such as the belief he expressed in his prediction) and desires (such as the
desire to win the prediction contest). So if the Martian sees the pattern in one Earthling, how can he fail
to see it in the others? As a bit of narrative, our example could be strengthened by supposing that our
Earthling cleverly learned Martian (which is transmitted by X-ray modulation) and disguised himself as
a Martian, counting on the specieschauvinism of these otherwise brilliant aliens to permit him to pass
as an intentional system while not giving away the secret of his fellow human beings. This addition
might get us over a bad twist in the tale, but might obscure the moral to be drawn: namely, the
unavoidability of the intentional stance with regard to oneself and one's fellow intelligent beings. This
unavoidability is itself interest relative; it is perfectly possible to adopt a physical stance, for instance,
with regard to an intelligent being, oneself included, but not to the exclusion of
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maintaining at the same time an intentional stance with regard to oneself at a minimum, and one's
fellows if one intends, for instance, to learn what they know (a point that has been powerfully made by
Stuart Hampshire in a number of writings). We can perhaps suppose our super-intelligent Martians fail
to recognize us as intentional systems, but we cannot suppose them to lack the requisite concepts.2 If
they observe, theorize, predict, communicate, they view themselves as intentional systems.3 Where there
are intelligent beings, the patterns must be there to be described, whether or not we care to see them.
It is important to recognize the objective reality of the intentional patterns discernible in the activities of
intelligent creatures, but also important to recognize the incompleteness and imperfections in the
patterns. The objective fact is that the intentional strategy works as well as it does, which is not
perfectly. No one is perfectly rational, perfectly unforgetful, all-observant, or invulnerable to fatigue,
malfunction, or design imperfection. This leads inevitably to circumstances beyond the power of the
intentional strategy to describe, in much the same way that physical damage to an artifact, such as a
telephone or an automobile, may render it indescribable by the normal design terminology for that
artifact. How do you draw the schematic wiring diagram of an audio amplifier that has been partially
melted, or how do you characterize the program state of a malfunctioning computer? In cases of even
the mildest and most familiar cognitive pathologywhere people seem to hold contradictory beliefs or
to be deceiving themselves, for instancethe canons of interpretation of the intentional strategy fail to
yield clear, stable verdicts about which beliefs and desires to attribute to a person.
Now a strong realist position on beliefs and desires would claim that in these cases the person in
question really does have some particular beliefs and desires which the intentional strategy, as I have
described it, is simply unable to divine. On the milder sort of realism I am advocating, there is no fact of
the matter of exactly which beliefs and desires a person has in these degenerate cases, but this is not a
surrender to relativism or subjectivism, for when and why there is no fact of the matter is itself a matter
of objective fact. On this view one can even acknowledge the interest relativity of belief attributions and
grant that given the different interests of different cultures, for instance, the beliefs and desires one
culture would attribute to a member might be quite different from the beliefs and desires another culture
would attribute to the very same person. But supposing that were so in a particular case, there
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would be the further facts about how well each of the rival intentional strategies worked for predicting
the behavior of that person. We can be sure in advance that no intentional interpretation of an individual
will work to perfection, and it may be that two rival schemes are about equally good, and better than any
others we can devise. That this is the case is itself something about which there can be a fact of the
matter. The objective presence of one pattern (with whatever imperfections) does not rule out the
objective presence of another pattern (with whatever imperfections).
The bogey of radically different interpretations with equal warrant from the intentional strategy is
theoretically importantone might better say metaphysically importantbut practically negligible once
one restricts one's attention to the largest and most complex intentional systems we know: human
beings.4
Until now I have been stressing our kinship to clams and thermostats, in order to emphasize a view of
the logical status of belief attribution, but the time has come to acknowledge the obvious differences and
say what can be made of them. The perverse claim remains: all there is to being a true believer is being
a system whose behavior is reliably predictable via the intentional strategy, and hence all there is to
really and truly believing that p (for any proposition p) is being an intentional system for which p occurs
as a belief in the best (most predictive) interpretation. But once we turn out attention to the truly
interesting and versatile intentional systems, we see that this apparently shallow and instrumentalistic
criterion of belief puts a severe constraint on the internal constitution of a genuine believer, and thus
yields a robust version of belief after all.
Consider the lowly thermostat, as degenerate a case of intentional system as could conceivably hold our
attention for more than a moment. Going along with the gag, we might agree to grant it the capacity for
about half a dozen different beliefs and fewer desiresit can believe the room is too cold or too hot, that
the boiler is on or off, and that if it wants the room warmer it should turn on the boiler, and so forth. But
surely this is imputing too much to the thermostat; it has no concept of heat or of a boiler, for instance.
So suppose we de-interpret its beliefs and desires: it can believe the A is too F or G, and if it wants the
A to be more F it should do K, and so forth. After all, by attaching the thermostatic control mechanism
to different input and output devices, it could be made to regulate the amount of water in a tank, or the
speed of a train, for instance. Its attachment to a heat-
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sensitive transducer and a boiler is too impoverished a link to the world to grant any rich semantics to its
belief-like states.
But suppose we then enrich these modes of attachment. Suppose we give it more than one way of
learning about the temperature, for instance. We give it an eye of sorts that can distinguish huddled,
shivering occupants of the room and an ear so that it can be told how cold it is. We give it some facts
about geography so that it can conclude that is probably in a cold place if it learns that its spatio-
temporal location is Winnipeg in December. Of course giving it a visual system that is multipurpose and
generalnot a mere shiveringobject detectorwill require vast complications of its inner structure.
Suppose we also give our system more behavioral versatility: it chooses the boiler fuel, purchases it
from the cheapest and most reliable dealer, checks the weather stripping, and so forth. This adds another
dimension of internal complexity; it gives individual belief-like states more to do, in effect, by providing
more and different occasions for their derivation or deduction from other states, and by providing more
and different occasions for them to serve as premises for further reasoning. The cumulative effect of
enriching these connections between the device and the world in which it resides is to enrich the
semantics of its dummy predicates, F and G and the rest. The more of this we add, the less amenable our
device becomes to serving as the control structure of anything other than a room-temperature
maintenance system. A more formal way of saying this is that the class of indistinguishably satisfactory
models of the formal system embodied in its internal states gets smaller and smaller as we add such
complexities; the more we add, the richer or more demanding or specific the semantics of the system,
until eventually we reach systems for which a unique semantic interpretation is practically (but never in
principle) dictated (see Hayes 1979). At that point we say this device (or animal or person) has beliefs
about heat and about this very room, and so forth, not only because of the system's actual location in,
and operations on, the world, but because we cannot imagine another niche in which it could be placed
where it would work (see also Dennett 1982/87 and 1987a).
Our original simple thermostat had a state we called a belief about a particular boiler, to the effect that it
was on or off. Why about that boiler? Well, what other boiler would you want to say it was about? The
belief is about the boiler because it is fastened to the boiler.5 Given the actual, if minimal, causal link to
the world that happened to be in effect, we could endow a state of the device with meaning (of a sort)
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and truth conditions, but it was altogether too easy to substitute a different minimal link and completely
change the meaning (in this impoverished sense) of that internal state. But as systems become
perceptually richer and behaviorally more versatile, it becomes harder and harder to make substitutions
in the actual links of the system to the world without changing the organization of the system itself. If
you change its environment, it will notice, in effect, and make a change in its internal state in response.
There comes to be a two-way constraint of growing specificity between the device and the environment.
Fix the device in any one state and it demands a very specific environment in which to operate properly
(you can no longer switch it easily from regulating temperature to regulating speed or anything else); but
at the same time, if you do not fix the state it is in, but just plunk it down in a changed environment, its
sensory attachments will be sensitive and discriminative enough to respond appropriately to the change,
driving the system into a new state, in which it will operate effectively in the new environment. There is
a familiar way of alluding to this tight relationship that can exist between the organization of a system
and its environment: you say that the organism continuously mirrors the environment, or that there is a
representation of the environment inor implicit inthe organization of the system.
It is not that we attribute (or should attribute) beliefs and desires only to things in which we find internal
representations, but rather that, when we discover some object for which the intentional strategy works,
we endeavor to interpret some of its internal states or processes as internal representations. What makes
some internal feature of a thing a representation could only be its role in regulating the behavior of an
intentional system.
Now the reason for stressing our kinship with the thermostat should be clear. There is no magic moment
in the transition from a simple thermostat to a system that really has an internal representation of the
world around it. The thermostat has a minimally demanding representation of the world, fancier
thermostats have more demanding representations of the world, fancier robots for helping around the
house would have still more demanding representations of the world. Finally you reach us. We are so
multifariously and intricately connected to the world that almost no substitution is possiblethough it is
clearly imaginable in a thought experiment. Hilary Putnam imagines the planet Twin Earth, which is just
like Earth right down to the scuff marks on the shoes of the Twin Earth replica of your neighbor, but
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which differs from Earth in some property that is entirely beneath the thresholds of your capacities to
discriminate. (What they call water on Twin Earth has a different chemical analysis.) Were you to be
whisked instantaneously to Twin Earth and exchanged for your Twin Earth replica, you would never be
the wiserjust like the simple control system that cannot tell whether it is regulating temperature,
speed, or volume of water in a tank. It is easy to devise radically different Twin Earths for something as
simple and sensorily deprived as a thermostat, but your internal organization puts a much more stringent
demand on substitution. Your Twin Earth and Earth must be virtual replicas or you will change state
dramatically on arrival.
So which boiler are your beliefs about when you believe the boiler is on? Why, the boiler in your cellar
(rather than its twin on Twin Earth, for instance). What other boiler would your beliefs be about? The
completion of the semantic interpretation of your beliefs, fixing the referents of your beliefs, requires, as
in the case of the thermostat, facts about your actual embedding in the world. The principles, and
problems, of interpretation that we discover when we attribute beliefs to people are the same principles
and problems we discover when we look at the ludicrous, but blessedly simple, problem of attributing
beliefs to a thermostat. The differences are of degree, but nevertheless of such great degree that
understanding the internal organization of a simple intentional system gives one very little basis for
understanding the internal organization of a complex intentional system, such as a human being.
3 Why does the intentional strategy work?
When we turn to the question of why the intentional strategy works as well as it does, we find that the
question is ambiguous, admitting of two very different sorts of answer. If the intentional system is a
simple thermostat, one answer is simply this: the intentional strategy works because the thermostat is
well designed; it was designed to be a system that could be easily and reliably comprehended and
manipulated from this stance. That is true, but not very informative, if what we are after are the actual
features of its design that explain its performance. Fortunately, however, in the case of a simple
thermostat those features are easily discovered and understood, so the other answer to our why question,
which is really an answer about how the machinery works, is readily available.
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If the intentional system in question is a person, there is also an ambiguity in our question. The first
answer to the question of why the intentional strategy works is that evolution has designed human
beings to be rational, to believe what they ought to believe and want what they ought to want. The fact
that we are products of a long and demanding evolutionary process guarantees that using the intentional
strategy on us is a safe bet. This answer has the virtues of truth and brevity, but it is also strikingly
uninformative. The more difficult version of the question asks, in effect, how the machinery which
Nature has provided us works. And we cannot yet give a good answer to that question. We just do not
know. We do know how the strategy works, and we know the easy answer to the question of why it
works, but knowing these does not help us much with the hard answer.
It is not that there is any dearth of doctrine, however. A Skinnerian behaviorist, for instance, would say
that the strategy works because its imputations of beliefs and desires are shorthand, in effect, for as yet
unimaginably complex descriptions of the effects of prior histories of response and reinforcement. To
say that someone wants some ice cream is to say that in the past the ingestion of ice cream has been
reinforced in him by the results, creating a propensity under certain background conditions (also too
complex to describe) to engage in ice cream-acquiring behavior. In the absence of detailed knowledge of
those historical facts we can nevertheless make shrewd guesses on inductive grounds; these guesses are
embodied in our intentional stance claims. Even if all this were true, it would tell us very little about the
way such propensities were regulated by the internal machinery.
A currently more popular explanation is that the account of how the strategy works and the account of
how the mechanism works will (roughly) coincide: for each predictively attributable belief, there will be
a functionally salient internal state of the machinery, decomposable into functional parts in just about the
same way the sentence expressing the belief is decomposable into partsthat is, words or terms. The
inferences we attribute to rational creatures will be mirrored by physical, causal processes in the
hardware; the logical form of the propositions believed will be copied in the structural form of the states
in correspondence with them. This is the hypothesis that there is a language of thought coded in our
brains, and our brains will eventually be understood as symbol manipulating systems in at least rough
analogy with computers. Many different versions of this view are currently being explored, in the new
research program called cognitive science,
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and provided one allows great latitude for attenuation of the basic, bold claim, I think some version of it
will prove correct.
But I do not believe that this is obvious. Those who think that it is obvious, or inevitable, that such a
theory will prove true (and there are many who do), are confusing two empirical claims. The first is that
intentional stance description yields an objective, real pattern in the worldthe pattern our imaginary
Martians missed. This is an empirical claim, but one that is confirmed beyond skepticism. The second is
that this real pattern is produced by another real pattern roughly isomorphic to it within the brains of
intelligent creatures. Doubting the existence of the second real pattern is not doubting the existence of
the first. There are reasons for believing in the second pattern, but they are not overwhelming. The best
simple account I can give of the reasons is as follows.
As we ascend the scale of complexity form simple thermostat, through sophisticated robot, to human
being, we discover that our efforts to design systems with the requisite behavior increasingly run foul of
the problem of combinatorial explosion. Increasing some parameter by, say, ten percentten percent
more inputs or more degrees of freedom in the behavior to be controlled or more words to be recognized
or whatevertends to increase the internal complexity of the system being designed by orders of
magnitude. Things get out of hand very fast and, for instance, can lead to computer programs that will
swamp the largest, fastest machines. Now somehow the brain has solved the problem of combinatorial
explosion. It is a gigantic network of billions of cells, but still finite, compact, reliable, and swift, and
capable of learning new behaviors, vocabularies, theories, almost without limit. Some elegant,
generative, indefinitely extensible principles of representation must be responsible. We have only one
model of such a representation system: a human language. So the argument for a language of thought
comes down to this: what else could it be? We have so far been unable to imagine any plausible
alternative in any detail. That is a good reason, I think, for recommending as a matter of scientific tactics
that we pursue the hypothesis in its various forms as far as we can.6 But we will engage in that
exploration more circumspectly, and fruitfully, if we bear in mind that its inevitable rightness is far from
assured. One does not well understand even a true empirical hypothesis so long as one is under the
misapprehension that it is necessarily true.
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Notes
1. The idea that most of anyone's beliefs must be true seems obvious to some people. Support for the
idea can be found in works by Quine, Putnam, Shoemaker, Davidson, and myself. Other people find the
idea equally incredibleso probably each side is calling a different phenomenon belief. Once one
makes the distinction between belief and opinion (in my technical senseDennett 1978a), according to
which opinions are linguistically infected, relatively sophisticated cognitive statesroughly states of
betting on the truth of a particular, formulated sentenceone can see the near triviality of the claim that
most beliefs are true. A few reflections on peripheral matters should bring it out. Consider Democritus,
who had a systematic, all-embracing, but (let us say, for the sake of argument) entirely false physics. He
had things all wrong, though his views held together and had a sort of systematic utility. But even if
every claim that scholarship permits us to attribute to Democritus (either explicit or implicit in his
writings) is false, these represent a vanishingly small fraction of his beliefs, which include both the vast
numbers of humdrum standing beliefs he must have had (about which house he lived in, what to look for
in a good pair of sandals, and so forth) and also those occasional beliefs that came and went by the
millions as his perceptual experience changed.
But, it may be urged, this isolation of his humdrum beliefs from his science relies on an insupportable
distinction between truths of observation and truths of theory; all Democritus's beliefs are theory laden,
and since his theory is false, they are false. The reply is as follows: Granted that all observation beliefs
are theory laden, why should we choose Democritus's explicit, sophisticated theory (couched in his
opinions) as the theory with which to burden his quotidian observations? Note that the least theoretical
compatriot of Democritus also had myriads of theory-laden observation beliefsand was, in one sense,
none the wiser for it. Why should we not suppose Democritus's observations are laden with the same
(presumably innocuous) theory? If Democritus forgot his theory, or changed his mind, his observational
beliefs would be largely untouched. To the extent that his sophisticated theory played a discernible role
in his routine behavior and expectations and so forth, it would be quite appropriate to couch his
humdrum beliefs in terms of the sophisticated theory, but this will not yield a mainly false catalogue of
beliefs, since so few of his beliefs will be affected. (The effect of theory on observation is nevertheless
often underrated. See Churchland 1979
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for dramatic and convincing examples of the tight relationship that can sometimes exist between theory
and experience.) (The discussion in this note was distilled from a useful conversation with Paul and
Patricia Churchland and Michael Stack.)
2. A member of the audience in Oxford pointed out that if the Martian included the Earthling in his
physical stance purview (a possibility I had not explicitly excluded), he would not be surprised by the
Earthling's prediction. He would indeed have predicted exactly the pattern of X-ray modulations
produced by the Earthling speaking Martian. True, but as the Martian wrote down the results of his
calculations, his prediction of the Earthling's prediction would appear, word by Martian word, as on a
Ouija board, and what would be baffling to the Martian was how this chunk of mechanism, the Earthling
predictor dressed up like a Martian, was able to yield this true sentence of Martian when it was so
informationally isolated from the events the Martian needed to know of in order to make his own
prediction about the arriving automobile.
3. Might there not be intelligent beings who had no use for communicating, predicting, observing, ...?
There might be marvelous, nifty, invulnerable entities lacking these modes of action, but I cannot see
what would lead us to call them intelligent.
4. John McCarthy's analogy to cryptography nicely makes this point. The larger the corpus of cipher
text, the less chance there is of dual, systematically unrelated decipherings. For a very useful discussion
of the principles and presuppositions of the intentional stance applied to machinesexplicitly including
thermostatssee McCarthy 1979.
5. This idea is the ancestor in effect of the species of different ideas lumped together under the rubric of
de re belief. If one builds from this idea toward its scions, one can see better the difficulties with them,
and how to repair them. (For more on this topic, see Dennett 1982/87.)
6. The fact that all language-of-thought models of mental representation so far proposed fall victim to
combinatorial explosion in one way or another should temper one's enthusiasm for engaging in what
Fodor aptly calls ''the only game in town".