The Southern Journal of Philosophy (1985) Vol. XXIII. No. I

IS KNOWLEDGE INFORMATION-PRODUCED BELIEF? A DEFENSE OF DRETSKE AGAINST SOME CRITICS Anthony Doyle Syracuse University

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In this paper I shall defend Fred Dretske’s informational analysis of knowledge against several recent criticisms. These criticisms shall bear on a central contention of Dretske’s Knowledge and rhe Flow of Information,l namely that knowledge is information-produced belief. Some of the objections discussed are more formidable than others, though none, it seems to me, is insuperable. Accordingly I would like to present them in the order of their formidability as 1 perceive it. The first two treated are taken from a commentary on a recent “Prtcis” that Dretske has written on his Knowledge.* They come from Carl Ginet and from Keith Lehrer and Stuart Cohen. Thence I would like to discuss a counter example of my own contrivance. The example 1 save for last is Gilbert Harman’s challenging example, which also forms part of the commentary on Dretske’s “Pr6cis”.

It shall be my purpose here to show-convincingly, I hope-that none of these decides against the thesis that knowledge is information- produced belief, and this because none of the true beliefs in question, alleged t o be knowledge on a Dretskean analysis, does in fact meet the necessary condition of being information-produced. What these objectors fail t o show, and what they must show if they are to produce a legitimate counter example to Dretske’s analysis, is that a situation can be envisaged in which someone a t once has an information-produced belief but would not be judged to know.

The issue that must be settled, especially as concerns Harman’s example, is, What is it for information to cause or causally sustain a belief? How can this abstract commodity be possessed of the efficacy needed to accomplish this? I t is this difficult topic which forms the last section of my paper. Unfortunately Dretske is distinctly reticent here. Nevertheless 1 think a full-bodied account can be teased out of the few and widely scattered remarks he does make. Before broaching this issue or discussing the just mentioned criticisms, however, I would like to

Anthony Doyle received his B.A. from Boston College in 1979, his M . A . from Northern Illinois University in 1984. and is currently studying for his Ph. D. in Philosophy at Syracuse University. This article was written while he was attending Northern Illinois University.

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rehearse briefly Dretske’s general view of information and then place his analysis in the Gettier context t o which it is in part a response.

A. In his preface to Knowledge and the Flow of Information Dretske serves notice that the theory of knowledge he is about to defend must be seen as a clean break with a great part of the epistemological past. Since he is seeking a naturalistic turf for his theory of knowledge, Dretske is among those concerned to leave off speaking of knowledge in terms of, say, justification, certainty, or evidence (Knowledge, p. VI11). Since he is convinced that Gettier has said the last word on the shortcomings of the justified true belief model of knowledge, an epistemology must be forged which does not rely on the just mentioned time-honored concepts. Of course the various causal theories of knowledge which have emerged in the wake of Gettier’s criticisms have likewise, in their naturalistic zeal, sought to avoid reliance on these traditional notions. And Dretske is clearly sympathetic with the causal project. Nevertheless he is convinced-for reasons that would take us far beyond the scope of the present exercise-that the causal theory has severe inadequacies of its own, inadequacies which can only be properly augmented by an appeal t o information. Hence before presenting his theories of knowledge, perception, belief, and concept formation it is incumbent upon Dretske to spell out his theory of information; the first three of Knowledge’s nine chapters are devoted to just this task.

Dretske is sanguine that his appeal t o information will provide his theory of knowledge with the objective basis that the notion of justification failed to provide the traditional model. Information, then, is for Dretske an objective commodity; and as a necessary condition for knowledge, the hope is that the latter can also be placed on objective ground. There is one other dividend which Dretske believes that his appeal to information will net him, one which shall be discussed at some length below, namely that the information analysis sheds new light on the controversial issue of relevant alternative possibilities and the claim that knowledge involves the exclusion of these.

B. A primary concern in Dretske’s chapter four, entitled “Knowledge,” is to show how the analysis of knowledge advanced here avoids ‘Gettier- like difficulties” or counter examples. Now as Carl Ginet points out, such avoidance can be understood in either the narrow sense in which “any account of knowledge which fails t o require the belief to be justified ips0 fact0 avoids such [Gettier-like] counter examples” (since on this interpretation Gettier counter examples can be generated any time there is justification for a false belief) or in the broader sense “in which a person with a true belief satisfies whatever further condition [in this case that the belief be information produced] but still fails to know” (“Precis,” p. 69). It can be safely supposed, 1 think, that Dretske’s

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resolve to escape Gettier-like difficulties is one sensible of this broader construal; it would be past belief, given the extraordinary pains that have gone into his analysis, that he intended to avoid Gettier counter examples in only the narrower sense. At any rate, as we shall see, his analysis is, so far as I can tell, Gettier-proof on either construal.

The upshot of Gettier’s criticism of the justified true belief model is that one can justifiably believe something that is true and yet not know it. As I just mentioned, Dretske for his part counts himself among those who are convinced that Gettier has permanently laid the justified true belief account t o rest. Although Dretske’s own analysis avoids any appeal to justification (when he does deign to discuss the notion, it is with thinly veiled disdain), it is withal sensitive to the possibility of Gettier-type counter examples. Let us look more closely atjust how it is Dretske believes he has achieved Gettier immunity.

If I may be permitted to invoke the traditional language for a moment, it can fairly be said that Dretske believes that his in- formational account avoids the pitfalls to which the justified true belief account is subject insofar a s the former, unlike the latter, refuses to sunder the evidence for our belief from what makes it true. We will recall that the demise of the traditional account lay in the very fact that it was possible to have perfectly good evidence for, and accordingly be justified believing in, something that was false. O n this basis, by the rule of disjunctive addition, it was possible to infer a true proposition for which one had no evidence. The result: a justified true belief that was not knowledge. 1 would now like to look brieflyat how Dretske believes his account can surmount this major difficulty of the justified true belief model.

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Following Alvin Goldman, Dretske wants to maintain that, at least with respect to perceptual knowledge, talk of the evidence that one has for one’s beliefs or whether or not one has “the right to be sure,” t o use Ayer’s phrase, is very much out of place. No longer should we demand of the perceptual knower that he be able to adduce “good reasons” for his knowledge claims. Nevertheless let us retain the traditional idiom forjust another moment and see how it applies to Dretske’s account. In the traditional parlance we might say that the information (say, that somethings has a certain property F) is evidence for believing, and thus knowing, that s is F. But this conception of evidence, appearing as it does in informational garb, marks a radical departure from evidence traditionally envisaged. What Dretske wants to say is that for a true belief t o qualify as knowledge there has not only got to beevidence, the belief in question must be bused on this evidence (Knowledge, page 86). To say that a belief is based on the evidence, i.e. the information that s is F, is t o say that it (the belief) could not possibly be false, since

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information, unlike evidence traditionally conceived, cannot be false. Belief which is properly caused or causally sustained by the information in question will perforce be knowledge. Hence Dretske’s analysis reads as follows:

K /perceptually/ knows that s is F iff I . s is F 2. K believes that s is F 3. K s belief is caused (or causally sustained) by the information

that s is F.3

In what remains particular attention, not surprisingly, will be paid to the third condition.

Dretske never tires of inculcating that if a belief is not suitably caused by the information that s is F (or if not initially caused by the information, comes later to be sustained by it) then the belief, though perhaps true and justified, will not be knowledge. Each of the counter examples of which I shall treat, I want to maintain, fails to take this third condition seriously; this is why none presents a genuine counter instance to the informational model of knowledge.

IV

Although several of the counter examples of which I a m about to treat are addressed by Dretske in his response to thecommentary on his “Prtcis,” and although his remarks there are helpful, they are also rather sketchy. Hence at the risk of repeating some of what Dretske says in his own defense I would like to bring his analysis more completely to bear on the problems they (i,e. theexamples) apparently identify. Let us look first at Ginet’s case.

Imagine, we are asked, a machine equipped with a red indicator light which shines if and only if the machine becomes too hot. A bystander, K , is curious about what the light, which happens at present t o be flashing, indicates. To find out he asks H, whom he has good reason to believe is an expert in such matters-though in this particular case as a matter of fact H knows nothing of the light’s purpose. However, H, not prepared to betray his ignorance in this instance, announces-with the voice of authority, let us suppose-that the red light means that the machine is too hot. K in turn forms the true belief that the machine is too hot. Ginet concludes that this case “satisfies Dretske’s sufficient condition for knowledge.” Why? Because K’s true belief that the machine is too hot “is caused by the information (carried by the light). . .” that the machine is too hot (“Prtcis,” p. 69).

N o w that the red light carries the information that the machine is too hot is not here under dispute. It clearly does. It carries the information because Ginet has stipulated that the machine’s being too hot is both a necessary and sufficient condition for the light to be flashing: if the light

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is flashing, the machine is too hot; the machine is too hot only if the light is flashing. Now this is consistent with Dretske’s theory of information. For the light to be carrying the information that the machine is over- heated the conditional probability of its flashing under this cir- cumstance must be one (or unity) and nothing less; the light’s flashing will for all intents and purposes be impossible if the machine is not hot; conversely whenever the machine is hot, the light will flash.

Imagine, however, the following counterfactual situation. The red light is ninety-eight percent reliable. Moreover it never fails to flash when the machine is too hot, and so never fails to warn those nearby of the possible danger. However, once in a blue moon-two percent of the time-the light flashes when the machine is at a perfectly normal temperature. What Dretske wants t o say here is that this light is by hypothesis incapable of yielding the information that the machine is too hot, and this because the conditional probability of the machine’s being too hot in this case is not one but only very high. Appropriating a term from information theory, Dretske sometimes describes a situation like this by saying that the light’s flashing is equivocal with respect to the machine’s being hot. In order for the information to flow equivocation must be eliminated, the conditional probability of the machine’s being over-heated must be one; until such time its flow is irretrievably obstructed. In Ginet’s case no such impediment exists, and so the light is capable of carrying the information.

However, the question at hand has bearing on a slightly different matter, for notwithstanding the fact that information is for Dretske an objective commodity, that it exists quite apart from knowing and believing beings, knowledge itself is not so context-free; whether or not the information is there, iffor K the conditional probability of the machine’s being too hot, given that the light is flashing, is not one, then he cannot under these circumstances know that the machine is too hot. Consequently to settle the issue of whether or not the light carries the appropriate information is only to settle the first issue. And we have just seen that this is not at present under dispute.

What is under dispute is whether or not it is this information that causes K’s belief. It does not-at least not completely. K’s belief, while partially caused by a signal which carries the information that the machine is too hot, is also partially caused by H, and his conjecture fails t o carry the information that the machine is too hot. H here, though perhaps ordinarily reliable, may be likened to the ignorant meddler of whom Dretske speaks in chapter four of Knowledge. 1 would like to say a word about this case.

For true belief to be knowledge Dretske demands that it be caused or at least sustained by the information in question. To bring this issue into bolder relief Dretske asks us to imagine an ignorant meddler whose word is never to be trusted as regards any matter of fact (Knowledge, pp. 89 ff.) Suppose now that the meddler, of whose wile we are unaware,

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having no knowledge himself, assures us that s is F. Suppose further that his assurances cause us to believe that s is F. Subsequently we find that s is indeed F. Question: d o we know in this instance? Dretske answers that we have knowledge here if and only if without the meddler’s assurances we would have believed that s is F, for in this circumstance the information now sustains our belief. If on the other hand we would not have formed our belief without the meddler’s assurances, we must be judged not to know. The result is entirely consistent with Dretske’s informational project: knowledge is information- produced belief, and if it is clear that no relation obtains between a true belief and the information for that belief, knowledge must be lacking.

To return to Ginet’s case, although H’s irresponsible assurances fail to carry the information that the machine is too hot, they nevertheless succeed in causing this belief in K. But it is just wrong to imagine, as Ginet precipitately does, that the information which the light in- disputably carries causes the belief.

However, Dretske is still not home free; it is still possible that K must be judged to know on the informational analysis. We will recall that in the ignorant meddler case just described it was still possible that someone could come to know nonwithstanding the fact that they had originally been induced to believe by a signal not carrying the information, since even after the meddler’s assurances one may come to know that s is Fif the information that s is Fsustains the belief. So Ginet could still urge here that although K’s belief is not properly caused by the information in question it is none the less properly sustained by it after K looks back a t the light. And given this informational support, he should be judged to know on Dretske’s account.

To settle this issue we must ask ourselves the same question that Dretske asks in chapter four of Knowledge: Would K in the absence of H’s assurances have believed that the light indicates a n over-heated machine? Fortunately there is no need to push our conjecture beyond the scope of Ginet’s case; the answer to this question is given there: K apparently did not have the slightest tendency, before consulting H , to believe that the light indicated that the machine was too hot. This was precisely why he asked H. K cannot bejudged to know on Dretske’s account because his true belief that the machine is too hot is neither caused nor sustained by the information in question.

The upshot here is that K’s true belief qualifies as knowledge if and only if in the absence of H’s assurances he would have believed merely on the basis of the flashing red light that the machine was too hot. NOW K’s belief was originally causedby H’s assurances, not the information. However, the crucial question here is, Would the sustaining in- formation, i.e. the red indicator light, have sufficed to bring about this belief in K? 1 think we have seen that in Ginet’s case the answer to this case is clearly No. Again: K knows if and only if this sustaining information alone would have brought about his true belief. If so, then

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his is an information-produced belief and accordingly he has knowledge. If not, then his true belief will not be knowledge because it is neither caused nor sustained by the information. Consequently although Dretske owns that knowledge can emerge even after the belief is not initially information-produced or caused, he insists that the sustaining information must be sufficient for the belief.4

Lehrer and Cohen present two counter examples, and since the second of these is more straight forward, I shall confine my discussion to it. Here a subject, Sopor by name (and tendency), finds himself in a “marvellous planetarium;” so marvellous in fact that “people report that often they cannot but believe that they are really seeing the heavens when inside”(“Precis,”p. 74). Furthermore it just so happens that there are small windows in its dome which, when opened on a clear and starry night, invariably lead people to confuse the projected illusions with real stars. Now Sopor, true to his name, falls asleep. When he wakes up, he utterly forgets that he is in a planetarium. He then sights a star shining through one of the planetarium’s windows and rightly believes it t o be a real star. Question: although we might be strongly inclined not to allow that Sopor has knowledge here, does he pass muster on Dretske’s account? Lehrer and Cohen think that he does; however, 1 think more attentive readers of the first five chapters of Knowledge would judge otherwise.

Dretske’s own response here is to the point. He denies that Sopor would know that what he is seeing is a star, reasoning that “a simulated point of light from the planetarium projector is a genuine alternative possibility, one that Sopor is. . . in no position to exclude on perceptual grounds” (“Prtcis,” p. 86). In other words there exists some relevant alternative (about which notion more shall be said presently) t o star S , let us call it S’, which, if it did obtain, Sopor would nevertheless have held fast to his belief that S. Normally of course when we gaze into the clear nighttime sky, the possibility of stars being simulations, indistinguishable from the real item, is not relevant. Hence it is not the kind of alternative we must be able to exclude in order t o have perceptual knowledge, though of course for Sopor and all others seated in this planetarium it is the kind of alternative that must be e x 6 d e d .

Let us also be mindful of the significance of the informational analysis here. Dretske will of course want t o say that the reason that Sopor does not know here is that the information that S is a star is not responsible for causing Sopor’s belief. The information-which is there whether it causes anything or not-could only have the needed efficacy if the conditional probability that what Sopor sees is a star is one (given the fact that he is seated in this remarkable planetarium). This is the significance of the definition Dretske gives of a signal’s informational content in chapter three of Knowledge:

Informational content: A signal r carries the information that s is F = the conditional probability of s’s being Fgiven r (and K ) , is 1 (but given Kalone is less than 1 ) (p . 65)

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( K here refers to the putative knower’s backround knowledge of the source.) Clearly the signal that Sopor is receiving is not one in which the conditional probability that S is a star is one. There a re relevant possibilities-possibilities whose conditional probability at the source is greater than zero-which the signal, given K , fails to exclude; the signal, because equivocal with respect to S’s beinga star, does not carry this information to Sopor. Now we should remember that the equivocation of a given signal will always be a factor of how we decide to carve up the possibilities at the source. We might, for example, provided that Sopor is sufficiently awake and a normal perceiver, say that he knows of S with respect to its beinga point of light with a certain color, since for this we may suppose that the conditional probability is one. Again, for the normal perceiver observing the starry sky there will still be a sense in which the signal is equivocal, and this depending on how we decide to carve up the possibilities at the source. For instance my experience of Sirius, while not equivocal with respect to its being a star, may be so with respect t o its being 8.3 light-years from earth. But this latter equivocation does not prevent me from knowing that it is a star, o r indeed that it is the brightest star in Canis Major.

Dretske, then, follows Goldman’s claim in the latter’s “Dis- crimination and Perceptual Knowledge,”5“that knowledge involves the exclusion of relevant alternative possibilities.” And we can now see why the former wants to claim that “knowledge inherits this property from information-theoretic sources” (Knowledge, p. 129). Knowledge so inherits this property because the flow of information-a necessary condition for knowledge-is impossible vis u . vis the belief in question until such time as all relevant possibilities have been eliminated and, accordingly, the conditional probability of the signal’s carrying the information that s is F is one. Once again, this is not to say that the information is not there all along, but that it will lack causal efficacy if, with respect to some believer, the conditional probability of s’s being F is less than one.

The next case I would like to discuss is one of my own design which, though 1 at first believed to be a counter instance to the informational theory of knowledge, 1 now realize can be handled quite easily on Dretske’s analysis. This example is based on one of Dretske’s own illustrations in chapter one of Knowledge. First, however, 1 must be permitted a short digression to discuss the important informational concept of bits.

In information theory the amount of information generated by or associated with a given state of affairs, in which the possibilities are all equally likely, is a factor of how many binary decisions, or bits, are required to eliminate these possibilities in order to arrive at the state of affairs in question. In other words the amount of information associated with an event or state of affairs, as Dretske explains in

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chapter one of Knowledge, is simply a factor of how many possibilities need be eliminated for that event to be the case. Suppose that we have eight equaliy likely possibilities, only one of which will come to pass. According to information theory the information generated by this alternative actually coming to pass is a factor of how many possibilities have been eliminated in order that it may come to pass. The method for calculating the amount of information--or bits-generated by a given state of affairs is as follows: we simply take the log of the number of equally likely possibilities which were reduced to one, in this case eight; now log 8 equals 3. Hence there are three bits of information generated by eight equally likely possibilities being reduced to one; three binary decisions are needed to make this reduction. All of this, I trust, will become clearer in the course of the following discussion.

In this case eight employees must decide among themselves which is to discharge a rather odious task for their employer. However, one in their midst, Shirley, is in poor health just now, so her solicitous colleagues decide ahead of time that if either she or Herman is chosen Herman’s name will be entered on the memo intended for the employer’s eyes. What this means in information terms is that a note bearing Herman’s name will carry only two bits of information generated at the source; it will carry the information that eight possibilities have been reduced to two, and this will be the information that Herman or Shirley was selected. Of course a note bearing the name of any of the remaining employees will carry three bits of information, since for their names to be entered eight possibilities must be reduced to one. As it happens, Herman is selected, and this selection, taken in isolation, may be described as a three bit event. But because of the convention adopted beforehand at the source, Herman’s name on the memo imparts only two bits of this information to the employer. Hence notwithstanding what the note says, the conditional probability of Herman’s being chosen, given the nature of the signal, is not one, but only .5. This means that the signal is incapable of carrying the three bit message that Herman was selected; it is equivocal with respect to his being selected. It can only carry the information for that state of affairs for which the conditional probability is one, namely that Herman or Shirley was chosen.

Now if this is all the information that the note carries, then this will be all the employer can learn from it; he cannot get the information for some act for which the conditional probability is less than one. And this indeed is the meaning of Dretske’s oft-repeated insistence that a signal carries just that information one can learn from it. Try to imagine now what will doubtless happen when the employer reads the note. There is every good reason to suppose that he will form on its basis the true belief that Herman was selected. Naturally if the employer has not been apprised of the code, he will believe that the note bears three bits of information. He will simply be wrong. I n no wise, Dretske insists, is the

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information that the note bears a factor of what the employer believes that it bears.

The stage is sufficiently set for the following attempted counter example. Suppose that the employer does form the three bit, non- informationally sanctioned belief that the note tells him that Herman has been chosen for the task. Then, for whatever reason, he infers and chooses to believe instead that Herman or Shirley was selected. We may imagine that our employer is a circumspect man in general, with a well-nigh pathological aversion to holding false beliefs in particular. Since he sees that this latter belief, while still quite specific, will more likely be true, he embraces it. 1 d o not think that we want to say that the employer knows here, for had the note actually carried the information that Herman or Donald was selected, there seems very good reason to say that he would have remained steadfast in his present belief. However, it is important that we look briefly at whatever reasons there might be for saying that the employer does know on Dretske’s analysis.

This disjunctive belief which the employer now affirms apparently has the benefit of an information support. After all, this belief corresponds exactly with the information contained in the note. Moreover it appears that the belief is information-produced, since a signal carrying the information stands a t the beginning of a causal chain which ends in the belief the information of which the note itself carries. N o ignorant meddler, for instance, has intervened. The note carries the information-this this much is beyond question-and the self same note is responsible for the employer’s belief-a belief which, happily enough, matches exactly the information carried. Should there not be knowledge on the information account?

I t is not difficult to imagine how Dretske would respond to a case like this. If the two bit relief is to count as information-produced, then the three bit belief from which it was inferred must also have been information-produced if the information link is t o remain intact. But it should by now be clear that the three bit belief was not-could not have been-information-produced, at least not by the right information; it was not because there were never three bits of information there in the first place. Consequently by the time the employer makes his two bit inferrence the information tether has been permanently severed. A further though not entirely happy consequence of denying that the employer knows here will be that so long as he is unaware of the unusual convention adopted at the source, he will be incapable of undergoing an information-produced belief. And so long as this is the case, the note’s informational properties will not be responsible for the belief that he happens to form. Hence Dretske’s analysis survives this example (at some slight cost, perhaps), for one could not know without the benefit of an information-produced belief.

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The primary assumption behind the Harman case-and I think it is a sound one-consists in this: “According to Dretske, a signal that K is aware of can carry the information without there being any way for K to determine what the information is” (“PrCcis,” p. 72). We have already seen my case bear witness to this fact. But, once again, the information is there to be had for the qualified receiver.

In Harman’s case we are again asked to imagine a situation where eight employees must be reduced to one. And here again Herman is the unlikely candidate. This time, however, it is not through the written word that the employees have chosen to inform their boss; rather, before the selection process was begun each employee was assigned a color, and it is on this basis that the information is imparted. The pink envelope’s arriving on the boss’s desk carries the information that Herman was chosen, since this was the color assigned him for that purpose at the source. Suppose now that the employer, having no knowledge of the convention adopted, forms the true belief that Herman was selected. He does this not out of any conviction that the envelope must carry this information, given the conditions obtaining a t the source-anyway such conviction is not necessary for knowledge on the informational account-but rather because it instead induces him to think of those hideous pink ties Herman insists on wearing. Harman wants to say here that it is the self same property-the pinkness-in virtue of which the information is carried which causes the employer’s belief.

This is the stiffest challenge to the information model I have seen. Is it not true that Dretske wants to tell us that if the information in a signal is t o cause a belief this must be by those properties in virtue of which the information is carried? Evidently it is difficult to avoid the conclusion that the employer has a n information-produced belief. Does Dretske endorse this conclusion? This is not a n easy question to answer, for he makes only the briefest mention of this case in his response: “If the employees are. . . reliable in their use of a pink envelope. . .” he announces,“then 1 don’t see why the employer couldn’t learn who was selected by the envelope’s color”(“PrCcis,” p. 84). Although this remark is not very helpful, I d o not take it to mean that Dretske intends to bite the bullet and agree that on his analysis the employer must bejudged to know. At any rate I think we can avoid this strange conclusion, and avoid it on Dretskean grounds. The solution, however, can only be given in the wider context of a discussion of the relation of a signal and the information it carries.

V

As mentioned above, it is incumbent upon Dretske to specify how it is that a n abstract commodity like information can be possessed of a causal efficacy, particularly in the context of an avowedly materialistic epistemology. Hence if knowledge is information-produced belief, the

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information-abstract commodity or not-must not be envisaged as subsisting apart from some material conditions. True enough, one and the same piece of information can find expression in any number of material guises; nevertheless there must be some physical property in virtue of which the information is carried.

1 mentioned in my introduction that Dretske is rather sparing in his remarks on this crucial issue. Notwithstanding this reticence, though, the several isolated remarks he does make shed important light on this matter. The most thorough attempt a t explaining the relation betweena signal, its information, and how this latter abstract commodity can cause a belief is given in chapter eight of Knowledge:

. . . what is meant by the information in a signal o r structure causing something to happen: information ( in a signal o r a structure[a note. say] causes E[a belief] insofar as the properties of S that carry the information a re those the possession of which by S make i t the cause of E. So , for example, if Scauses the information that s i s F a n d this information is carried by means of S's having the property G . then we may say that if S's being Gcauses E then the information [that S carries] that s is Fcauses E(pp . 198-199).h

It is this account, 1 am optimistic, which is competent to lay to rest the very challenging objection of Harman. However, as i t stands, it is obviously in need of some determined unpacking. I propose to d o this by means of the spy/courier case Dretske presents in chapter four of Knowledge.

I n this case a spy's belief that a certain courier has arrived is described as being caused by the information that the courier has arrived, and this in virtue of the special sequence of the knocks (and not, for example, in virtue of their pitch or in virtue of the materials that the door happens to be made out of). If the instances of the present example are substituted for the account just quoted, we get the following results. I f the signal, S, i.e. the sound, carries the information that s is F, i.e. that the courier has arrived, and this information is carried in virtue of the signal's having a certain property. G-in this case the special sequence of the knocks- then we can say that if the signal's being G is what causes belief E, then (and only then) the information that s is Fcauses belief E. The courier case clearly meets these conditions. The sequence of the knocks is sufficient to cause the belief: under "relevantly similar circumstances" where the knocks were sounded the spy would have formed the belief that the courier has arrived. Moreover the sequence is necessary for this belief; no other sequence of knocks would have begotten the belief that the courier has arrived. If just any sequence of knocks could have begotten this belief, even if the courier were the one doing the knocking (in which case the belief will still be true), the knocks will not carry the information that the courier has arrived, for under these circumstances the conditional probability of the courier's having arrived will not be one. We may suppose, a t most, these knocks carry the information that surneone is a t the door. since the conditional probability for this is one.

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But the information the knocks carry will be incapable of causing any more specific belief than this.

Another feature of information’s causal efficacy, also pointed out by Dretske, must be noted briefly. Suppose that the special sequence (and only this sequence) causes in the spy not the belief that the courier has arrived, but something else instead. Would it still be proper under these circumstances to speak of the information’s causal efficacy? Dretske thinks it would. Imagine, he asks us, that the knock code causes the spy to panic. In this case we are entitled to say that the information that the courier has arrived causes the spy to panic if and only if just this sequence of knocks gives rise to the spy’s panic. “If, on the other hand, it is merely a knock on the door that causes the spy to panic. . . then the information that the courier has arrived is not the cause of panic” (Knowledge, p. 88). We might say here that the information that someone is at the door is what causes the spy to panic.

We must also imagine a situation where the intelligence officials have failed to apprise the spy of the knock code. Suppose now that the spy hears the special knock and on its basis forms the true belief that the courier has arrived. Here we have a case where the spy’s belief t h a t p is caused by a signal bearing the information tha tp . Does the spy know on Dretske’s account? 1 d o not think that he does, for under these circumstances there is every good reason to suppose that the chambermaid’s knock would have engendered the same belief. Consequently it is not those properties in virtue of which the knock carries the information that the courier has arrived that cause the spy to believe this; any old knock would have sufficed.

We can now see why the Harman case is not a genuine counter example. Harman wants t o say that the self same property in virtue of which the signal carries the information, in this case the pinkness of the envelope, is also what causes the employer’s true belief that Herman was selected. And this on the face of it seems true enough, since it is precisely the pinkness which triggers the true belief. Hence we have a signal which indisputably carries the information, and that property in virtue of which it does so causing the belief in question. Have we met with an information-produced belief or, more precisely, with a belief produced by the right information? Once again, I d o not think that we have. To see why we must ask a question which Harman himself does not ask, Is it the case that the employer would have believed that Herman was selected even if the envelope had not carried this information?

- We should remember that there is an element of convention-that established at the source, among the employees-associated with the fact that a pink envelope carries the information that it does. Imagine that the pink envelope, whose color corresponds to property G in the rather long passage cited on page 44, had not carried the information that Herman was selected. Now in order to be assured that the information and not merely the envelope’s pinkness causes the belief we

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must first be assured of the following: in a situation where the pink envelope did not carry the information it would not have caused the belief in question. In other words if the belief that Herman has been selected would have been brought about in the employer by a pink envelope, where this did not carry the requisite information, then we can say that its pinkness alone-and not the information it embodies- is the cause of the belief. I think we search in vain for such a n assurance from Harman; a pink envelope carrying the information that, say, Shirley was selected, combined with the stipulation that no other color but pink could have begotten the employer’s conviction that Herman was the nominee, could nevertheless havecaused the belief that Herman was selected. Consequently the information does not cause the employer’s belief.8

v1 In this paper 1 have tried to defend Dretske against counter examples

of varied toughness. However, if the truth be known, I am not completely confident that I have done justice to his position at every turn. Moreover it is an unfortunate consequence of Dretske’s analysis that it seems as if information’s efficacy is to a great extent context-dependent. Still, I d o not think that this seriously undermines the radical objectivity for information which he is so anxious to secure. Finally it must be said that if I have been right in supposing that his analysis withstands the challenges presented here this testifies in large measure to its resilience.s

NOTES

I (Cambridge: MIT Press. 1979). Hereafter referred to as Knowledge. 2 “Precis” of Knowledge and the Flow of Information, Behavioraland Brain Sciences 6

3 Dretske nowhere gives his analysis of knowledge in just this form. Nevertheless I

4 I have adopted several referee’s suggestions in this paragraph. 5 See his “Discrimination and Perceptual Knowledge,” Journal q/ Philosophy 20

(1983). pp. 55-90. Hereafter referred to as “Prk is .”

believe this to be an adequate statement of what it amounts to.

( 1976). pp. 770-79 1 . S here refers to the signal. The discussion in this paragraph owes much to a referee’s comments.

8 I would like 10 thank Ray Molitor for suggesting the Gettier-inspired title and Professor Michael Tye for his encouragement and his many comments on an earlier draft of this paper. 1 would also like to thank Jane Carter for her extraordinary patience at the typewriter. I

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