Causal Theories of Knowledge1

MIDWEST STUDIES IN PHILOSOPHY, IX (1984)

Causal Theories of Knowledgel FRED DRETSKE AND BERENT ENC

ausal theories of knowledge require some causal connection between belief Cand the conditions whose existence make that belief true. Lacking this connection, the belief may be true, it may be altogether reasonable, but it is not knowledge. Philosophers have a variety of reasons for imposing this requirement. Aside from its intrinsic plausibility in cases of perceptual knowledge, the condition has a solid, naturalistic ring to it. It does a fair job in avoiding Gettier-type examples; it helps fix the object of belief; it shows promise as a device for avoiding skepticism and foundational regresses; and it bids fair to capture the intuition that a belief, to qualify as knowledge, must have no admixture of accidentality in its correspondence with the facts. Whatever the reason, many philosophers have endorsed some version of the causal theory. Our purpose in this essay is to examine the basic elements of a causal theory. We shall argue that it isn’t clear whether a causal theory can do the job it is supposed to do, but, if it can, some fundamental revisions must be made in the role the causal condition plays in the production of belief. The following is a first formulation of a causal condition on knowledge. It isn’t intended to be complete. It is, at best, a base clause in most formulations of the causal condition. Nevertheless, it represents the causal theory in its purest form, and it is the pure form of this theory that (allegedly) applies to our clearest cases of knowledge (e.g., perception). C(0): S knows that P only if the fact that P is the cause of S’s belief that P. I can see (hence, know) that I have five fingers on my right hand only if the fact that I have five fingers on my right hand causes me to believe this. Though we commonly talk of events-and sometimes facts-as the cause of things, these modes of description tend to obscure important distinctions that are, we believe, vital to an appropriately formulated causal analysis of knowledge.

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Consider the cause of Tom’s intoxication. On Tuesday afternoon, Tom drinks a quart of clear liquid. The liquid in question happens to be gin, a 94 proof liquid. We have one event (fact?) referred to (expressed?) in different ways: Tom’s drinking a quart of clear liquid and Tom’s drinking a quart of gin. Since it is the event itself (however we may happen to refer to it) that enters into causal relations, it seems to follow that it was Tom’s drinking a quart of clear liquid on that afternnon that caused him to become intoxicated. This, though, isn’t right. What causes Tom’s intoxication is not his ingestion of a quart of clear liquid, but hisingestion of a quart of gin. In drinking a quart of gin he drinks a quart of clear liquid, but the former, not the latter, is (what we will call) the effective cause. If Tom’s ingestion of a quart of clear liquid is (because the liquid in question is gin) the same event (fact?) as his ingestion of a quart of gin, then we need some way of specifying the causally effective or causally relevant elements of this single event (or fact). The notion of an effective cause is our way of doing this. To see why this distinction is important for a causal theory of knowledge, consider Sally’s allergy to lecithin-a substance found in milk and egg yolks and often added to chocolate bars. Sally has noticed that whenever she eats chocolate, she breaks out in a rash. After a dinner party, noting the distinctive rash beginning to appear, she comes to believe that there was chocolate in the food. In fact, there was chocolate (with lecithin) in the mole sauce served with the chicken. The chocolate in mole sauce doesn’t really taste like chocolate and it is hard to detect. Nothing else Sally ate contained lecithin. Under the circumstances, it seems clear that Sally does not know that the food contained chocolate. Is the fact that there was chocolate (with lecithin) in the food Sally ate the same fact as that there was lecithin (in the chocolate) in the food she ate? Is her ingestion of the chocolate with lecithin in it the same event as her ingestion of the lecithin in the chocolate? These questions do not seem to have clear answers. What is clear is that if these facts (or events) are the same, then we need a more discrirn- inating way of referring to the cause of belief. We can, of course, refer to the event that caused Sally’s rash (and resulting belief) with any of the following expressions: Sally’s eating the mole sauce, Sally’s eating the chocolate (in the mole sauce), Sally’s ingesting the lecithin (in the chocolate). And since her belief that the food she ate contained chocolate was caused by the event these expressions pick out, it was, it seems, caused by her eating the chocolate. But though these expressions pick out the same event (token), her belief that the food she ate contained chocolate is distinct from her belief that the food she ate contained mole sauce or lecithin. A causal theory of knowledge should, therefore, prescribe different causes for these different beliefs. To do this one needs a finer grained analysis of the causal condition, an analysis that looks to those properties of the event that make it a causally effective agent. The food’s containing chocolate (with lecithin) is not what caused Sally’s rash (and subsequent belief). It isn’t (what we are calling) the effective cause. The effective cause was the food’s containing lecithin (whether or not in chocolate). The food’s having chocolate in it is causally irrelevant-its only relevance being that, as a matter of fact, this particular chocolate had lecithin in it. CAUSAL THEORIES OF KNOWLEDGE 519

Describing the cause as an event or fact (without focusing on the effective properties) obscures these essential distinctions. Speaking of effective causes is merely a way of shifting from an extensional to an intensional mode of discourse about events and causes, a way of referring to event tokens that exhibits their relevant type affiliation and thereby reflects the lawful regularities that underly their causal power. The event token, c, has its effects (the rash, Sally’s belief) by virtue of being a realization (instance, token) of a certain property (event ype)-the ingestion of lecithin-and there is, under the circumstances, some causal regularity between events of that type and such effects.2 It may be thought that we are putting a burden on the causal condition that it was not designed to bear. It isn’t that C(0) is wrong or too weak. Rather, what disqualifies Sally’s belief (that there was chocolate in the food) as knowledge is not the failure of the causal condition, but the failure of some other condition on knowledge. Perhaps, that is, Sally fails to know there was chocolate in the food because she has a false background belief, the belief that only chocolate produces the rash, and a correct analysis of knowledge requires, besides a causal condition, some condition excluding the presence of false background beliefs. The exclusion of false background beliefs may be required at some point in the proceedings, but we don’t think it is relevant here. The causal theory has the resources for handling this case without invoking other conditions. What disqualifies Sally’s belief (as a form of knowledge) is not that she has a false background belief, but that this false belief affects her causal relationship to the world-thereby dis- qualifying her on causal grounds. Compare: what makes the instrument inaccurate is a faulty spring, but the spring is responsible for the instrument’s inaccuracy only because it changes the way the world affects the instrument-changes the way the instrument responds to external conditions. If that didn’t change, the faulty spring would be irrelevant. And so it is with false background beliefs. They are relevant to the acquisition of knowledge, but only because they influence the way we causally interact with the world. A false background belief merely makes it more difficult to satisfy the causal condition on knowledge. C(0) should therefore be reformulated to reflect this more discriminating specification of the cause. The causally effective properties must be made explicit. We do so by abandoning the factive and adopting the gerundive mode of specifying the cause: something’s being F, turning G,ingesting H, or whatever. We also, in order to avoid unnecessary complications, restrict ourselves to de re beliefs. C(1): S knows of u that it is F only if a’s being F is the cause of S’s believing of a that it is F. Sally doesn’t know that the food contained chocolate because it was not the food’s containing chocolate that (via the rash) caused her to believe this. It was the food’s containing lecithin. Hence, Sally fails to satisfy C(1). C(l) forces one to distinguish between a house’s being painted blue and a house’s being painted Toby’s favorite color even when blue is Toby’s favorite color. Even though we have one event (or fact?) described in different ways, we have two 520 FRED DRETSKE AND BERENT ENC

(potentially) effective causes (or event types): its being painted blue and its being painted Toby’s favorite color. This is a distinction a causal theory of knowledge needs. For we surely want to make distinctions, cognitive distinctions, between two beliefs, one of which is caused by Q’S being painted blue, the other of which is caused by Q’S being painted Toby’s favorite color. The causal conditions on knowing that Q is blue are not the same as knowing that Q is Toby’s favorite color. Though an improvement, C(l) is still inadequate. Not only does it fail to cover what Alvin Goldman calls Type I1 cases: it also fails to accommodate obvious counterexamples involving overdetennination. If I am caused to believe that a patient will soon die by observing massive, and inevitably fatal, brain damage, I know he will die (other possible conditions being satisifed) even though I am not caused to believe he will die by his impending death. Rather, his death is caused by a condition that causes me to believe he will die. I am causally connected to the condition I believe will obtain (patient’s death), but not in the way described by C(1). Instead, I am caused to believe of Q that it will be F by a condition, massive brain damage, that causes Q to be F. We could, following Goldman, supplement C(1) to include this more indirect type of causal relationship. This would be premature. For one can know the patient will soon die even if he is hit by a truck as he leaves the hospital and dies from the injuries sustained in this accident-even if the massive brain damage that causes one to believe he will die does not cause his death. This, of course, is merely a version of Brian Skyrms’s example: If a man dies of poisoning and is later beheaded, his death is not causally related to his decapitation. He died of poisoning. Yet, one can know he is dead by observing his decapitated state. One knows a condition ob- tains to which one’s belief bears no causal relationship. Such examples have convinced some that a causal condition is much too de- manding. It isn’t that there must actually be some causal connection (however indirect) between the belief and the condition believed to obtain. Instead, the belief may be caused by some condition (event, state) that, though it doesn’t actually cause the condition believed to exist, is causally sufficient for it. So, for example, if one is caused to believe that the patient will die by the presence of massive brain damage, then one knows he will die even if the brain damage doesn’t actually cause death. It is enough that it would cause death if nothing else did. It seems to us that some modification of the causal theory along these lines is necessary. A pure causal theory, one requiring an actual causal connection between Q’S being F and the belief that a is F, cannot be sustained. It is enough, and perhaps within the spirit of a causal theory, if the cause of belief is a causal guaran- tor of the truth of that belief. In cases where the belief that Q is F is caused, not by Q’S being F, but by a condition (b’s being G) that is causally sufficient for Q’S being F, we will speak of the cause (of belief) as being a causal surrogate for a’s being F. Modifying C(l) ac- cordingly gives: C(2): S knows of Q that it is F only if S’s belief of Q that it is F is caused by (a) 11’s being F or (b) some causal surrogate of Q’S being F. CAUSAL THEORIES OF KNOWLEDGE 52 1

It is important to emphasize, though, that whether we are speaking of the condition itself, or some causal surrogate for it, it is the effective cause that figures essentially in the satisfaction of C(2). As we saw in the case of Sally, she failed to know that the food contained chocolate because it wasn’t the food’s containing chocolate that was the effective cause of belief. And in cases where a causal surrogate is operating, it must be the surrogate’s effective property (that property whose realization makes the event an effective cause) that figures in both the event’s causation of belief and in its sufficiency for (13being F. To illustrate this with a Type I1 case, suppose Clarence sees Tom drink a quart of gin and is caused to believe by this observation that Tom will soon be drunk. A pure causal theory, a theory that looks to the actual causal relations exist- ing between events in a given situation, would reach the judgment that the causal condition was satisfied by Clarence’s belief. Yet, if Clarence does not see that (or otherwise know that) it is gin that Tom is drinking, if it isn’t Tom’s drinking one quart of gin that causes Clarence to believe this, then C(2) renders the verdict that Clarence does not know that Tom will get drunk. The condition that causes him to believe that Tom will soon be drunk must be the condition that is sufficient for Tom’s getting drunk.’ By giving Clarence what turns out to be true background beliefs (e.g., the belief that the bottle contains gin), we make him susceptible, so to speak, to only the right causes. Seeing Tom drink one quart of gin is not enough to know that Tom will get drunk, not if the effective cause of this belief is Tom’s drinking one quart of liquid. To satisfy C(2), one needs a discriminating network of background beliefs, a network of background beliefs that “tune” one to those properties of the event that are causally responsible for Tom’s getting drunk. Justificationalists may insist, as a further condition, that Clarence’s belief about what it is that Tom is drinking be somehow justified. Reliability theorists may be willing to dispense with this ad- ditional requirement. But the point remains that C(2) makes the kind of discrimina- tions one expects of a causal condition on knowledge. It is a way of capturing, within the spirit of a causal theory, what Nozick was after in requiring an ability to “track” the world! This same point can be made with a Type I case. If Clyde’s fuel gauge functions properly on weekdays but not on weekends, does Clyde know he needs gas when he consults the gauge (reading “empty”) on Tuesday? Once again, a causal condition [e.g., C(O)] that ignores effective causes gives the wrong answer. Since (it may be supposed) it is the fact that the tank is empty that causes the gauge to register “empty” and this, in turn, causes Clyde to believe his tank is empty, the causal condition is satisfied. But C(2) requires us to judge this case otherwise. If Clyde is unaware of the gauge’s erratic behavior, if he trusts it every day of the week, if, in other words, it is the gauge’s reading “empty”, not its reading “empty” on a weekday that is the effective cause of belief, then Clyde does not satisfy C(2). To satisfy C(2), it is not enough that the gauge read “empty” on what is, in fact, a weekday and that its reading “empty” cause Clyde to believe he is out of gas. The property of the gauge that is causally sufficient for an empty tank (reading “empty” 522 FRED DRETSKE AND BERENT ENC on a weekday) must actually be the property of the gauge in virtue of which it cauSes Clyde to believe. Clyde is being caused to believe by a condition which, under some description, is causally sufficient for an empty tank, but it isn’t under that description that it functions as a cause of Clyde’s belief. C(2), then, appears to be an improvement on less analytical (and, hence, less discriminating) statements of the causal condition on knowledge. By abandoning the requirement of an actual causal connection (no matter how indirect) while re- taining (in the notion of a causal surrogate) the idea of causal sufficiency, and by insisting on the importance of an event’s effective properties in the articulation of the causal relationships, C(2) yields a better fit with the data without altogether losing touch with the original spirit of the causal theory. We must now confront a problem that plagues all causal theories. For we sometimes come to know that a is F by a condition or state of affairs (b’s being G) that bears no causal relation to a’s being F, fails even to qualify as a causal surrogate of a’s being F. We are not thinking of familiar difficulties causal theorists have with mathematical, general, and abstract truths (does 2 t 2 being 4 cuuse you to believe that 2 t 2 is 4?). There are problems enough with empirical knowledge of particular facts. We are thinking, instead, of situations in which b’s being G is a reliable (perhaps only a locally reliable) sign of a’s being F when this reliability is not a manifestation of any cuusal regularity. That is, within certain environments there seem to be de facto, noncausal correlations that are sufficiently extensive and unexceptional (in those environments) to confer on b’s being G the power to produce a knowledge that a is F. Think of our ability to recognize automobiles by their silhouette and styling. Does the car’s being an Oldsmobile cause it to have that silhouette and styling? Ap- parently not, since some Oldsmobiles don’t look like that. Is its having that appearance a causal surrogate of its being an Oldsmobile? No, since we can easily construct a forgery. Nevertheless, if, as a matter of fact, no other car looks just like that particular model Oldsmobile, why isn’t this fact alone (quite aside from the question of whether this fact is a manifestation of a cuusal regularity) enough to enable one to recognize it as an Oldsmobile? Face recognition exhibits the same pattern. I recognize my uncle by his face although his having that face and his being my uncle are causally unrelated. His having that face, the one by means of which I recognize him, could be the result of a disfiguring accident. A frog’s cognitive capacities exhibit a similar structure. Lettvin et al. have identified the effective properties of the stimulus in the production of the frog’s response to flying insects.’ What causes the frog to flick at the flying bug with its tongue is the bug’s projecting (to the visual receptors of the frog) a small, dark, moving profile. Anything exhibiting these visual properties will do. Carefully produced shadows that are used in the laboratory turn out to be as effective in trigger- ing the response as bugs are in the frog’s natural habitat. The frog’s (so-called) bug detectors, those systems of neurons that have their optimal firing rate to this kind of visual stimulus, are bug detectors only by grace of the fact that in the creature’s natural surroundings only edible bugs exhibit that constellation of properties. But CAUSAL THEORIES OF KNOWLEDGE 523 something’s being a small, moving, dark spot is not causally sufficient for its being an edible bug. The shadows show that. And the creature’s being an edible (to the frog) bug does not cause it to be a small, moving, dark spot. Dead bugs are perfectly edible and they don’t move. The frog doesn’t recognize them. Something’s being a small, moving, dark spot plays the same role (in the frog’s recognition of bugs) that one’s uncle’s face plays in recognizing him as one’s uncle.’ Or consider Tinbergen’s well-known studies of the stickleback fish. During the mating season, the males turn a bright red on their underside.’ Males use this feature to recognize male intruders, and females use it to identify interested males. The fish react this way to a variety of objects of similar coloration: artificial wooden models eliciting aggressive behavior in the males and sexual interest from the females (a red mail van passing the window of the laboratory provoked similar behavior). Tinbergen notes that “the stickleback responds simply to ‘sign stimuli,’ i.e., to a few characteristics of an object rather than the object as a whole. A red fish or a red mail truck, it is the signal, not the object, that counts.”’o This is a fairly primitive form of recognition, of course, but is it much different (aside from number and complexity of characteristics involved) from the way we identify the sex of people we meet? It illustrates nature’s way of solving an epistemological problem. There are no red “models” (much less mail trucks) in the stickleback’s natural habitat. As long, therefore, as there are no other objects with this peculiar coloration, nature can economize on the cognitive resources it devotes to satisfying the organism’s needs. The “sign stimuli” are enough. It is a matter of indifference whether there is a causal connection between having a red underside and being a male stickleback. What is important is that the fish’s sensitivity to this characteristic developed because it was, at least in the fish’s natural surroundings, a reliable index to the presence of a male conspecific. It may be objected that frogs and fish don’t have beliefs. Hence, their so-called cognitive exploits are irrelevant to a theory of knowledge. Perhaps. But the causal theory is an attempt to naturalize knowledge, and if, for whatever reason, we do not yet have knowledge at this biological level (because, for example, we don’t yet have beliefs) we surely expect to find the kind of natural relations between organism and environment that will confer upon beliefs, once they arrive on the evolutionary scene, the status of knowledge. Even if one insists on a justificational account of knowledge, the frog surely has (without being able to exploit it as a justification) as good a justification for thinking there is an edible bug in the vicini- ty as we have for most of the things we purport to know. Nature adopts the most economical strategy in designing systems to satisfy their needs. So do engineers. If a system needs F’s, and hence requires the cognitive wherewithal to recognize F’s, it is enough to design a system to recognize G’s if, in point of fact, only F’s are G in the system’s sphere of operation. Furthermore, it is clear that for the purpose of this design problem, it is irrelevant whether in that sphere of operation this correlation between F and G is a symptom of some underlying causal regularity. Why build a fuel gauge whose responses are limited, specifically, to gasoline in the tank when one that will respond the same to any 524 FRED DRETSKE AND BERENT ENC

Ziquid in the tank will, given the normal operation of the gauge, serve as well? The fact that our automobile gauge cannot distinguish between gasoline and water in the tank does not prevent us from learning what we need to know (that there is still some gas left) from the gauge. (Once again, it is irrelevant to point out that it is gasoline in the tank that is causing the gauge to register “full”; the point is that it is not its being gasoline that causes this.) If it requires a greater expenditure of cognitive effort to distinguish F’s from non-F’s than it does to distinguish G’s from non- G‘s, it would be profligate of nature (or an engineer) to design a system for which a’s being F was the effective cause when a’s being G will do the job. And it will do the job as long as the system in question remains in an environment in which there exists this correlation between F’s and G’s. Why complicate the frog’s nervous system to enable it to distinguish real bugs from deceptive shadows when such hard- ware is irrelevant to the frog’s efficiency in its natural surroundings? If mock (un- edible) bugs start to appear in swamps and ponds (exhibiting the same effective properties as bugs now do), nature will see to it that either the requisite means of discrimination develops or that frogs will vanish from swamps and ponds. To retain their fitness, frogs will need a new mechanism, one that is sensitive to more subtle, discriminating properties of the stimulus. The same can be said about the stickleback. These considerations suggest that the causal factors associated with knowledge, if they are to be found at all, must sometimes be found in the etiology of those mechanisms that now enable an organism to know something from which it is causally insulated. If a belief that a is F is produced by b’s being G, and the causal unrelatedness of b’s being G and a’s being F does not itselfprevent this belief from being knowledge, then perhaps this is because the cognitive structures responsible for this disposition themselves have the right causal antecedents. Natural selection, through processes that are fairly well understood, has “tuned” organisms to be sensitive to properties, in their environment that are (locally) reliable signs of other properties that the organism needs to detect, recognize, and respond to. This tuning process sometimes exploits noncausal correlations to achieve its ends. Exposure to these correlations leads to the development of mechanisms in members of the species that enable them to satisfy their needs by responding to properties that are not necessarily causally related to the satisfaction of these needs. The long time span, the magnitude of the numbers involved, and the high price paid by false starts require that the correlation responsible for the development of these mechanisms be a widespread and prolonged one. Spurious correlations, those not persisting throughout the geographical range and temporal duration of the species’ evolution, will not be causally effective in shaping such cognitive dispositions. The learning process occurring in the lifetime of an individual is in some ways similar to the adaptive development of a population. Certain relationships, the persistent co-occurrence of F with G, produce a change in the organism’s cognitive dispositions: i.e., in its tendency to believe (anticipate) that a is (will be) F upon perceiving b to be G. Our earlier examples of recognizing a person by his face ana a car by its styling was meant to illustrate this phenomenon. As learning theorists like to put it, the contingencies between stimuli (the degree of co-occurrence of F and CAUSAL THEORIES OF KNOWLEDGE 525

G) produce a change in the organism’s pattern of responses-a change, if you will, in the function mapping stimuli onto beliefs (or responses). One learns to recognize coffee cups, trucks, and umbrellas. One does so by acquiring a sensitivity to certain properties that are (often) only locally correlated with the condition whose presence one learns to recognize. Philosophers are fond of pointing out that many of our ordinary concepts are functional concepts. To be a coffee cup, a truck, or an umbrella is not to have a certain shape, color, and size. It is to function, or be used (or be designed to be used) in a certain sort of way. Yet, though such objects are not classified in accordance with their sensible properties, we use these sensible properties in identifying them. One can see that a is a coffee cup, not because one sees it being used in a way a thing must be used (or usable) to qualify as a coffee cup, nor because one apprehends the intentions of its designer, but because it has the kind of sensible properties that, as a matter of fact, only things of that (functional) kind have. Knowing that a is a coffee cup in this way is no different than a stickleback’s recognition of another stickleback. We each exploit properties of the object whose correlation with the object’s being as we believe it to be has produced in us (by evolutionary adaptation in the case of the fish, by learning in our case) the requisite sensitivity. If things go right, our cognitive dispositions have the right cause. Where does this leave us? Our discussion suggests yet another modification of the causal condition on knowledge, something along the following lines: C(3) S knows of a that it is F only if S’s belief of a that it is F is caused by (a) a’s being F or (b) a causal surrogate of a’s being F or (c) some condition (b’s being G) whose effective property’s (i.e., G’s) correlation with F has produced in S the disposition S manifests in acquiring this belief. This is still a causal condition of sorts. The final clause (c) is merely a causal condition on the background beliefs that “map” (current) stimuli onto (current) beliefs. We are, however, very reluctant to propose this as even a partial analysis of knowledge. The whole structure is getting too creaky and unwieldy. It threatens to collapse under its own weight. Can such a monstrous condition possibly be a condition on knowledge? We doubt it. Furthermore, the suggested change departs significantly from the kind of intuitions that originally motivated a causal theory of knowledge. If this is a causal theory of knowledge, it certainly isn’t what most philosophers will recognize as the causal theory of knowledge. Finally, we are uncertain about whether causal theorists shouldn’t be content with a causal condition on background beliefs alone. That is, the drift of our argument has been, implicitly, an argument against the necessity of C(2). If it is, as we argued, the fact of correlation (within an organism’s environment), not the causal or lawful grounding of this correlation, that is responsible for the development of those cognitive mechanisms on which an organism depends to satisfy its needs, then it is, or should be, this same fact that figures in a naturalized picture of knowledge. 526 FRED DRETSKE AND BERENT ENC

If it is the correlation, whether causal or not, that is responsible for the development of cognitive systems exhibiting a “displaced” sensitivity (a sensitivity to something’s being G when what the organism needs, or needs to know about,is F), then it should be these correlations, not their causal foundation, that is relevant to evaluating the organism’s cognitive condition. But if this is so, the causal connection [expressed in clauses (a) and (b) above] between individual beliefs and their satisfaction conditions turns out to be irrelevant. The relevant question is whether the correlations that make a belief reliable were themselves instrumental in shaping the cognitive mechanisms that determine what and when an organism believes. That is, the relevant question is whether (c) is satisfied. Nevertheless, despite our uncertainty on this matter, we think that something resembling C(3) is the best chance, perhaps the only chance, a causal theory has for giving a realistic picture of knowledge. So let us close by mentioning one counter- intuitive, but (we think) perfectly acceptable, consequence of clause (c) in C(3). Consider the following situation: Toby lives on the Island of Elysium, geographical- ly and ecologically isolated from the rest of the world. In Elysium all yellow fruit contains citric acid. There are, for example, no bananas on the island. Addition of citric acid causes milk to curdle. Curdled milk is the basic ingredient of the most popular cheese in Elysium, and Toby’s family has been in the business of producing curdled milk for cheese manufacturers for many years. They have handed down the secret of making curdled milk from generation to generation. The “secret,” though, happens to be that the juice of any yellow fruit will curdle milk, something that is (considered literally) false though, when applied to the yellow fruit on that island, true enough. What promoted this belief, of course, is the repeated (and vaned) suc- cess in curdling milk with the juice of yellow fruit. Toby, preparing to curdle the batch of new milk, believes, as he has always believed, that the milk will curdle. What causes him to believe this is his careful extraction of the juice he is using from some yellow fruit-lemons in this case. What causes the milk to curdle is not the additive’s being the juice of yellow fruit. It is the additive’s containing citric acid that causes this. So Toby’s (false) background belief makes him sensitive to something (being the juice of a yellow fruit) that is neither the cause, nor is it a causal surrogate for, the condition (curdling of the milk) he expects to occur. Yet, given the unexceptional correlation between the juice of a yellow fruit and its milkcurdling powers on that island, and given the fact that it was the existence of this persistent correlation over generations that caused Toby to have this background belief, it seems to us altogether reasonable to say that Toby knows the milk will curdle. The similarity between this case and the lecithin example is instructive. In each case, the agent’s belief that a is (will be) F is caused by a property that is causally unrelated to a’s being F. In Sally’s case, however, the correlation between something having chocolate in it and the appearance of her rash was largely coincidental. Many things not having chocolate in them would produce the rash. Sally just hasn’t eaten them. Nevertheless, two properties F and G that are not persistently correlated in a person’s natural environment may, for whatever reason, be perfectly CAUSAL THEORIES OF KNOWLEDGE 527 correlated in that person’s experience. As a result, the person (like Sally)may become disposed to believe that something is F upon encountering an instance of G. The causal antecedents of Sally’s disposition are no different than the antecedents of Toby’s disposition. Both have experienced a uniform correlation. Why, then, say that Toby knows but Sally doesn’t? Since, in natural selection, the stakes are so much higher (survival? extinc- tion?), it is difficult to find organisms whose genetically coded dispositions are analogous to those of Sally. But we find a variety of creatures in Toby’s condition. The difference is partly a matter of degree, something having to do with the extent and reliability of the correlations that produced in one the disposition to believe. Such issues are familiar ground in epistemology. The attention given to “relevant alternatives” and “defeasibility conditions” is a symptom of the importance of this issue. But there are deeper intuitions operating in distinguishing Toby’s from Sally’s condition. It is, we think, the biological paradigms that function in our classifica- tions of epistemological reality. Toby knows, whereas Sally doesn’t, because Toby is more like the frog and the stickleback than Sally. If nature had designed a cognitive system for Toby, one to be used in the satisfaction of (let us imagine) a biological need to curdle milk, nature would have yielded precisely what we find in Toby -a sensitivity to the color of fruit. That is all nature did for the frog and the stickleback. Why should it do more for Toby? And if nature wouldn’t have done it any different, who are we to demand higher design standards? But Sally is a different matter. If she had a biological need for chocolate, her reliance on the rash would be short-lived indeed. If we are correct in thinking that the biological examples form a paradigm for our ascriptions of knowledge, then the problem of relevant alternatives ought to be approached by a causal theorist by looking to see how closely each case ap- proximates that paradigm. One has to ask what the natural environment is and, secondly, whether, if there were genuine biological needs at stake, a continued disposition of thar kind in that environment would long survive.

Notes 1. Our thanks to David Sanford for helpful comments on an earlier draft. 2. The distinction we have in mind here was made by J. L. Mackie in terms of the difference between “explanatory causes” and “producing causes” (see his The Cemenr of the Uni- verse [Oxford, 19741, 26268). Mackie writes, “We can . . . say that the concrete event, this hammer blow, was the producing cause of the chestnuts’ change of shape, it was what actually led on to this change; but the explanatory cause was the fact that there was a blow of at least such-and-such a momentum . . , . The concrete event was not necessary in the sense in which the fact was; the event could have been different without altering the result, whereas the fact as stated could not” (265). Mackie goes on to note that explanatory causes generate opaque contexts, whereas producing ones are purely extensional. Our reference to effective causes is a way of talking about Mackie’s explanatory causes. But we don’t like the word “explanatory.” It suggests that the cause is an artifact of our explanatory or epistemic stance- hence, something unavailable for the analysis of such epistemic concepts as knowledge. Reference to effective causes is relevant to explanation, but not because reference to such causes is covertly a reflection of our epistemic attitudes. Rather, a causal 528 FRED DRETSKE AND BERENT ENC explanation is (among other things) an attempt to identify the relevant connection between cause and effect- to identify, in other words, the effective cause -those properties of theevents whose lawful relation underlies their causal relationship. Elliott Sober has a helpful discussion of a closely related distinction in “Why Logically Equivalent Predicates May Pick Out Different Properties,” American Philosophical Quurterly 19(April 1982). Sober argues, rightly we think, that expressions like “Sally’s eating the chocolate” (not his example) are ambiguous between a rigid and a nonrigid designation of the property in question. 3. Alvin Goldman, “A Causal Theory of Knowing,” Journal OfPhilosophy 64(1967):357- 72. 4. Brian Skyrms, “The Explication of ‘Xknows that P’,” Journal of Philosophy 64(1967): 37 3-89. 5. A causal theroy of perception, a theory about what Clarence sees, need not advert to effective causes. For if Clarence sees Tom drinking a clear liquid, and the liquid in question is gin, then (whether or not Clarence knows it) he sees Tom drinking gin. But knowledge, seeing that Tom is drinking gin, is different. We return to this point again. 6. Robert Nozick, Philosophical Explnnutions (Cambridge, Mass., 1981), 178. 7. J. Y. Lettvin, R. R. Maturana, W. S. Maulloch, and W. H. Pitts, “What The Frog’s Eye Tells the Frog’s Brain,” Proceedings ofthe Institute of Radio Engineers 47( 1940-195 1). 8. In the frog’s natural surroundings, of course, it is (usually) a nearby bug that causes the frog to believe (or, if this is too strong, to respond as if) there is a bug newby. But this, as we have argued, is irrelevant. It is also gin that Clarence sees Tom drinking. This doesn’t mean that Clarence is in a position to know that Tom is drinking gin. What is of relevance to a causal theory of knowledge (though not to a causal theory of perception - i.e., what objects and events we perceive) is whether its beinga bug (its being gin) is the effective cause of belief. 9. N. Tinbergen, “The Curious Behavior of the Stickleback,” Scientific American, Decem- ber 1952; reprinted in Frontiers of Psychological Research (San Francisco). 10. Frontiers of Psychological Research, 9.