Externalism and Memory

     This relative neglect of the question of whether externalism applies to memory-contents seems to me unfortunate. For one thing, it leaves us without a proper understanding of the conditions of individuation of mental content generally. For another, the applicability of externalism to memory bears upon certain objections that have recently been raised to phenomenal externalism (the view that the phenomenal qualities of experiences are one and the same as certain externally individuated representational properties).² Finally, it is sometimes taken for granted that the externalist account of memory has very counter-intuitive consequences. Whether this is really so merits careful examination.

     So, are memory-contents partly individuated by external factors? In this paper, I shall argue that anyone who is sympathetic to Twin-Earth thought experiments for externalism with respect to certain thoughts should endorse externalism with respect to certain memories.³ I shall also argue that the apparently paradoxical character of externalism, as applied to memory-contents, dissolves under close analysis. My discussion is divided into four sections. The first explains how my use of the term ‘content’ is to be understood. The next two sections make out the case for memory externalism. The final section addresses counter-arguments and concerns to which the view gives rise.

     Some philosophers individuate PA-contents more coarsely than I have above, as, for example, sets of possible worlds. On this view, the thought that all vixens are foxes has the very same content as the thought that 7 + 5 = 12. However, it seems intuitively undeniable that the event type, thinking that all vixens are foxes, plays a different role in rationalizing explanation than the event type, thinking that 7 + 5 = 12. So, on this approach, thought-types cannot be individuated for the purposes of rationalizing explanations by their contents alone. Two different thought-types can have the same content. Likewise for other PAs.

     The difference between these two views of thought-content seems to me largely verbal. Which view to adopt seems basically a matter of deciding how one wants to use the word ‘content’. I will use the term ‘content’ throughout the paper, as it is applied to PAs generally, as in the former fine-grained approach.⁴

     My primary focus in the case of memory will be upon propositional memory and the content of memory, so understood. But I certainly will not be denying that there are memory images of things. Memory images are discussed further in Section IV.

     Putnam’s Twin-Earth is a planet as much like Earth as possible except that the liquid there that is called ‘water’, that comes out of taps and fills lakes, and that is colorless, tasteless, and odorless, is not H2O but XYZ.⁵ Following Putnam, it seems to me plausible to say that this liquid on Twin-Earth is not water but something else that superficially resembles water—twater, as it is often called. Generalizing, it seems plausible to claim that what makes a given sample an instance of a given natural kind (e.g., water) is not its appearance, its superficial properties, but its underlying microstructure. This claim is not universally accepted, of course, but for present purposes I shall assume that it is correct.

     With this much background in place, let us begin with the following thought-experiment: I am on Earth, holding a flagon of water in my hand. I sincerely utter the sentence, “I drank two pints of water from a flagon yesterday without pausing.” My molecular twin, on Twin-Earth, utters the very same sentence. He has never left Twin-Earth, just as I have never left Earth. Neither of us has engaged in any fanciful space travel to bizarre alternative planets. So, he has never seen or tasted or causally interacted with any samples of water, just as I have never done any of these things with respect to twater. In these perfectly mundane circumstances, my twin surely has as much right to be credited with an accurate memory as I do. It cannot be correct to say (in English), then, that his memory is veridical if and only if he drank two pints of water yesterday from a flagon without stopping. Rather the accuracy-conditions for his memory must advert to twater. It follows that memory-contents can differ in microphysical duplicates. External factors are relevant to the individuation of memory-contents.

     In the example just given, my past environment is the same as my present one, and likewise for my twin. What it shows directly is that past external factors—ones that obtained at the time that the memory representation was laid down—are relevant to the individuation of memory-contents expressible in that-clauses that utilize natural kind terms. The example does not yet show that present external factors can override past ones. So, it can still be held that where present and past environments came apart (through travelling), what determines natural kind memory-contents is the past environment.

     Even so, the above claim is not one that would be universally accepted. The thesis that microphysical duplicates can differ with respect to the contents of their memories, as I am understanding it, is not like the thesis that microphysical duplicates can differ with respect to what they see—at least if the term ‘see’ is taken to be a success verb. Given that one cannot see X, unless X exists, it trivially follows that one’s seeing X does not supervene upon purely internal factors. In the case of the term ‘memory’, however, at least as I am using the term, having a memory that p does not entail that p. It could be the case, for example, that I did not drink two pints of water yesterday without pausing, that my memory is inaccurate. Likewise for my twin and his twater memory. Still, the contents of our mistaken memories (‘mismemories’, if you like) are individuated, in part, by external factors. And that is a substantive externalist thesis.

     But what if past and present environments come apart? Which external factors determine content then? Consider next the case in which I sincerely say to you, “Water is the only thing I now drink before 5pm. Many years ago, however, I drank water fortified by gin in the afternoons. I enjoyed those afternoons—water is improved by mixing it with gin.” Suppose that, unknown to me, I am now on Twin-Earth, and that I have been for a long time so that I have established the environmental connections needed for new thoughts and beliefs. In these circumstances, my word ‘water’, as it is used in the first sentence of my report, means twater. The belief it expresses—a belief about my present environment is a belief that involves the concept twater. In the second sentence, ‘water’ again is most plausibly taken to mean twater even though the report concerns the past. For if ‘water’ here means water, then I am not comparing my present drinking of twater with my past drinking of it. And that seems plainly wrong. Intuitively, the concept I exercise when I use ‘water’ in the second sentence refers to twater, the very stuff upon which I directed my opening remark. Intuitively, what I am saying, indeed what I believe if I am sincere, is that twater is the only thing I now drink before 5pm, even though many years ago, I drank twater fortified by gin in the afternoons. In the third sentence, I explain why I enjoyed those distant afternoons by adding that twater is improved by mixing it with gin.⁶ This would make no sense if what I really believed is that I drank water with gin during those afternoons. My remarks, it seems, are based upon an inaccurate memory. Many years ago on Earth, before I switched to Twin-Earth, I drank water, not twater, before 5pm.

     The conclusion to which we seem drawn is that where past and present environments come apart, natural kind concepts entering into the contents of propositional memories get their extensions determined by the present environment. This is a strong externalist thesis about memory. It implies, for example, that memories are not always laid down with their contents fixed and then later retrieved. Instead, their contents can float free of the settings that gave rise to them and change with suitable changes in the external setting.

     It might be replied that the above example does not adequately support this conclusion. Suppose I am informed that I am now living on Twin Earth, and that I have been for some years. Suppose also I believe my informant. Would I not now correct my previous remarks by saying that I had mis-spoken and that I really believed that I had drunk (Earth) water in my youth? Would I not claim that what I had wanted to say was that many years ago I had drunk (Earth) water with gin in the afternoons?

     Certainly, I wanted to tell the truth. And now knowing the real facts, I realize that I did not drink twater in my youth. But until a few moments ago, I firmly believed that I had never switched planets. At the time I made my remarks, I also believed that I was on Twin-Earth (for I used the term ‘Earth’ to refer to the same planet as everyone else in my linguistic community). So, I certainly believed that twater was what I used to drink just as it is now. Given the new information, then, my beliefs about the past change; I no longer believe what I did. So, I wouldn’t now say what I did. However, at the time I said what I believed.

     Perhaps it will be granted that I believe that twater was not the only thing I used to drink before 5pm. And perhaps it will also be granted that I take myself to have a twater memory (i.e., a memory that involves the concept twater). Still, it might be said, intuitively, what I really remember is that I used to drink water with gin before 5pm. My belief that I have a twater memory is in error. On this view, externalism is true for the contents of certain beliefs about the past just as it is for the contents of certain beliefs about the present; but it is not true (in any strong sense) for memory contents.

     The obvious objection to this reply is that if externalism holds for some beliefs about the past, then it can hardly fail for some thoughts about the past. After all, it is normally supposed that, in believing that p, one assents to the very content one entertains in thinking that p. Moreover, it is a simple matter to modify the above thought-experiment so that it applies directly to thought rather than to belief.⁷ But if externalism is true for any thought-contents pertaining to the past, then it must surely also be true for the corresponding memory contents (and, in particular, for the memory content that I drank twater with gin before 5 pm), since intuitively, it is part and parcel of remembering that p that one think that p.⁸

     Another reason not to accept the above reply is that it flies in the face of privileged access. We are self-conscious beings. We have the capacity to know what we are thinking and to do so, it seems, in a way different from the way in which we know what others are thinking. We normally have a direct and authoritative access to what we are thinking, to the contents of our thoughts. Likewise for the contents of our conscious propositional memories. Given privileged access of this sort, if I occurrently remember that so-and-so, then I am capable of knowing what I am remembering without any empirical investigation of my environment, provided that I able to exercise the normal human capacity to have beliefs about my occurren memories (and allowing mismemories to count as memories).⁹ It cannot be the case, then, that in the above example I believe that my memory-content is that I used to drink twater with gin before 5pm when, in reality, my memory-content is that I used to drink water before 5pm.¹⁰

     A third objection is that while I do indeed believe that I used to drink twater with gin, it is also true that I believe that I used to drink water with gin. Once the slow switch has been completed, I am subject to both beliefs. My mistake is to suppose that water is the same as twater.

     That, however, is very implausible for at least two reasons. For one thing, after many years on Twin-Earth I surely am not prepared to apply both the concept twater and the concept water to the liquid that comes out of taps, fills lakes, etc in my current environment. (I certainly don’t believe that, in this case, there is water around here.) For another, if on Twin-Earth, I perform a Putnam thought-experiment in reverse with respect to Earth, I would surely deny that there is any twater on that planet while simultanously granting that water is found there. How could I do that, if I believed that water is twater?

     A fourth objection is that what the example really shows is simply that I mistakenly think that my present thoughts, beliefs, memories concerning the past in the above case use the same natural kind concept as the corresponding propositional states concerning the present. In reality, two different concepts expressed by ‘water’ are operative.

     This again is unsatisfactory. Consider my final remark in the example. Here I express my belief that twater is improved by mixing it with gin. I take the content of that belief to explain why I enjoyed certain past afternoons. Given that I have the usual access to what I believe (something no externalist worth his salt will deny), it seems obvious that I cannot rationally offer such an explanation, unless I believe that I drank twater with gin on those afternoons. It is also worth noting that the objection is straightforwardlly at odds with what is prima facie a very plausible thesis, namely that a person can always know authoritatively and directly with respect to any two of his present thoughts or beliefs whether or not they have the same contents. In my view, this comparative thesis, which is obviously a close cousin of the privileged access thesis for individual thought contents, is not one that the externalist has any need to deny.¹¹

      A final objection is that the proposed position simply does not do justice to the strong intuition that there are past episodes I have not forgotten in the described case. For I surely retain some memory impressions or images of myself drinking water and gin in past afternoons. This last claim seems to me correct as far as it goes. But it concerns memory impressions or images of water rather than propositional memories into which the concept water enters. So, it does not undermine the conclusion I have tried to establish thus far, namely that anyone who is moved by Putnam’s Twin-Earth thought experiments to embrace externalism with respect to certain thought-contents pertaining to the present (specifically, those expressible in that-clauses into which natural kind terms enter) should hold a parallel externalist position with respect to the corresponding memory-contents. The two positions seem to me to stand or fall together.¹²

     I turn next to Burge’s social externalism, as applied to memory.

     On the basis of his own Twin-Earth thought experiments, Burge (1979) argues that if a thinker is a member of a linguistic community, then if the thinker exercises a deferential concept in thinking that p, then the content of the thought is individuated partly by socio-environmental factors (where these factors include the relevant linguistic conventions).¹³

     Here is a Burge-type Twin-Earth thought-experiment that is a little simpler than his well-known arthritis example.¹⁴ (forthcoming (a)). The extension below to the case of memory is mine alone. Suppose that when Tom, a freshman student in one’s introductory logic class, is asked to define ‘validity’ and ‘soundness’, he responds “An argument is sound if and only if were all of its premises true, its conclusion would be; and an argument is valid if and only if it is sound, and all of its premises are true.” If Tom is expressing his actual belief, then he has made a conceptual mistake: he has confused validity and soundness; and thus his belief is false. One would correct him and he would, presumably, defer and accept the correction. However, we can imagine a possible world that contains an intrinsic physical twin of Tom who is a member of a community that speaks a language just like English, except for the fact that in that language, Twin-English, ‘validity’ is used as we use ‘soundness’, and ‘soundness’ is used as we use ‘validity’ (and, of course, except for any other differences that logically follow from this difference). Twin-Tom would express a true belief if he answered the Twin-Earth teacher by saying, “An argument is sound if and only if were all of its premises true, its conclusion would be; and an argument is valid if and only if it is sound, and all of its premises are true.” For what he would be saying, translating into English, is just what people who speak English and who properly understand validity and soundness would say, if they were asked to define them, in that order one after the other. Thus, while Tom has a false belief involving a conceptual mistake, Twin-Tom, in contrast, has a true belief. Yet Tom and Twin-Tom are intrinsic physical twins.¹⁵

     This reasoning can be extended to cover the case of memory. Suppose that Tom is now a senior and he is asked whether he remembers what he was told four years ago in his introductory logic class about the distinction between soundness and validity. He replies, “I was told that an argument is sound if and only if were all its premises true, its conclusion would be; and an argument is valid if and only if it is sound, and all its premises are true.” Tom’s memory is inaccurate. That is not what he was told. Twin-Tom, however, in giving the same reply to his teacher on Twin-Earth, has an accurate memory; for he is speaking Twin-English. So, their memories differ even though they are intrinsic physical duplicates.

     In this example, there is no shift in environment through time. Suppose next then that Tom is whisked off to Twin-Earth without his realizing it immediately after taking his introductory logic class. Once there, he initially uses the terms ‘valid’ and ‘sound’ in talking about arguments in the way that is correct on Earth, but as time goes by, his usage of these terms comes to conform to those that are established on Twin-Earth without his realizing that any shift in meaning has occurred. Later in his life, Tom still vividly recalls his introductory logic teacher’s squeaky voice, and his oft-repeated remark, “Once again, your argument is not valid,” though he has forgotten nearly everything else that his teacher said. Tom’s teacher did use those words, but they did not mean what Tom now means by then. The remark of Tom’s teacher was concerned solely with the reasoning in his students’ arguments. But that is not how Tom now understands it. Intuitively, Tom now misremembers what his teacher said.¹⁶

     Tom’s mismemory is induced by the change in his social environment. Had Tom never left Earth after taking introductory logic, in recalling his teacher’s words, he would have had an accurate memory of their content. Error arises in the travelling case, since Tom becomes a full-fledged member of another linguistic community, and (at the time of recall) he is speaking Twin-English. The concept Tom expresses by the word ‘valid’ on Twin-Earth is not the one he used to express by that word on Earth. Tom’s memory on Twin-Earth draws on his later concept, and thereby it leads him astray. It follows that memory-contents can be fixed, at least in part, by the social setting (and in particular the linguistic conventions) at the time of the episode of recall.

     Cases not unlike the imaginary one just described are found in real life. The term ‘wasp’ in American English describes a large black stinging insect much larger than the one which the British call ‘wasp’. ‘Wasp’ in American English picks out what ‘hornet’ picks out in the Queen’s English; and wasp’ in the Queen’s English picks out what ‘yellow-jacket’ denotes in American English. Some months ago, I was stung by several wasps (and here I am writing in American English). Afterwards, lying in bed in some pain, I recalled my mother exclaiming to me many years earlier in my youth, “There is a wasp nest in your bedroom. Do not go in there!” As I ‘heard’ her remark again echoing through my mind, I misrembered its content. I grew up in Britain; so ‘wasp’, as my mother used it, meant yellow-jacket. But that is not what I thought she had meant as I recalled her comment. At the time, my ‘memory’ was that she had been talking about wasps as I would now, speaking American English.

     Here, then, is a real-life case in which memory-content changes with change in social environment.¹⁷ And there are any number of other examples of a similar sort. For it is generally agreed that the meanings of words can change over a long period of time without one noticing the change. Thus, in any case in which one recalls a linguistic auditory image one had in the past, one will misremember its content, if there has been a suitable change in the meanings of one’s words.

     Reflection upon examples like that of Tom suggests that Burge’s social externalism is as applicable to memory-contents as it is elsewhere.¹⁸ Anyone who accepts social externalism for certain thought-contents on the basis of Burgean Twin-Earth thought experiments is going to be very hard-pushed to deny that certain memory-contents also fall within its scope.

     One concern some philosophers express about externalism with respect to memory is that it makes memory defective in travelling cases.¹⁹ The externalist is committed to supposing that once one shifts one’s environment, one can no longer rely on one’s memory to tell one about certain features of the past.²⁰ More strongly, the externalist is committed to supposing that in the relevant cases, one’s memory must lead one astray. But intuitively, one’s memory should work as well as before. For there has been no neurological impairment, indeed no neurological change of any sort pertinent to memory.

     This worry seems to me to derive largely from an equivocation on the meaning of ‘defective’. Consider a machine that has been built to detect bombs. In the context in which it is first used—to single out bombs in luggage at airports before the advent of plastic explosives—it works extremely well. But later on, as non-metallic bombs are placed in luggage, it becomes ineffective. The design of the machine is such that in one setting it functions well, but in another setting it fails. In a sense, it becomes defective: for it no longer succeeds in doing what it was designed to do. Still the hardware continues to operate smoothly. There are no mechanical breakdowns in the running of the machine. Given a suitcase with a metallic bomb in it, the machine responds to it effectively just as it did when it was first introduced. In a second sense of the term ‘defective’, then, the machine is not defective.

     Likewise, in the case of memory. Shifting environments does not make memory defective in the hardware sense. The internal physical systems that are relevant to memory continue to work just as they did in the original environment. But shifting environments can make memory defective in the broader design sense. Since the new environment can create mismemories, on the externalist account,—and indeed must do so, given the appropriate external changes—facts outside the head in the new environment can prevent one from remembering facts one knew at an earlier time, even though physiologically nothing has changed. In such circumstances, memory, considered as a psychological capacity, fails to perform the function for which it was designed: for it fails to inform one correctly about facts concerning the past.

     Another charge that is sometimes levelled against externalist theories of memory is that they lack an adequate explanation for how a person, S, through travelling from one environment to another, can fail to know at a time, t2, what she was thinking at an earlier time, t1 (Boghossian 1989). The obvious reply is that with the shift, S simply forgets something she knew before.²¹ This may seem strange if one takes the view that that one forgets something—the name of the inventor of bifocals, say—only if it slips one’s mind, only if upon being asked, one ‘goes blank’. For clearly nothing of this sort happens in any of the cases described in the last two sections. Tom, for example, has an immediate and vivid ‘memory’ of what his introductory logic teacher really said. Still, Tom does misremember certain facts. In this sense, he forgets. He is, in this way, like the person who, upon being asked how far the earth is from the sun, says with strong conviction that it is 39 million miles, when he originally knew that the distance is 93 million miles. Here, it seems to me correct to say that the person has forgotten the distance—not because he cannot produce an answer at all but because he has an inaccurate recollection.

     Perhaps it will now be said that even if externalism is appropriate for remembering that so-and-so is the case, it does not apply to memory images of things or events. Take, for example, the case of visual memory images. The worry here is easy to grasp, if one endorses a photographic conception of such images. For if visual memory images represent in the manner of photographs, then their contents are frozen in time, fixed by the contents of the original perceptual representations that gave rise to them. Travelling from one environment to another can makes no difference. What travelling does is to alter the traveller’s beliefs about his or her memory images.

     However, there is, I maintain, no good reason to adopt a photographic model for visual memory images. For one thing, it does not seem to fit the facts of introspection. Intuitively, my visual memory image of the ripe apples I saw in the kitchen earlier today has no intrinsic, non-intentional, introspectible features. It is transparent or diaphonous.²² The image itself isn’t red any more than my present visual experience is, as I look at a red pen-cap lying on the desk before me. The memory image represents the apples at the earlier time as red. The qualities it represents the apples as having are the only features to which I have access when I introspect the image just as in the case of the externally produced visual experience. Introspective attention to a memory image, then, is not like viewing a photograph. Only the content is accessible.

     Secondly, the photographic conception of visual memory images is also incompatible with what we know about how such imagery actually works. For example, it has been found that when people are asked questions about famous faces—whether, for example, Clark Gable or George C. Scott has bushier eyebrows—those who reported having the most vivid memory images tend to be the least accurate.²³ This makes perfectly good sense if generating a memory image is a conceptually driven process, something like producing a sketch or a drawing. For if the instructions in memory that govern the production of the drawing are partial or incomplete, subjects who have vivid images must fill in the gaps themselves at the time of recall without recourse to stored representations of the missing facial features of the relevant people. But if generating a memory image is a matter of retrieving a stored photograph, it is very hard to see what could account for the relative inaccuracy of the vivid imagers.²⁴

     Still, even if the photographic model is abandoned, it might be insisted that intuitively travelling cannnot alter what some memory images are images of. For example, suppose one day in Spain I happen to see Margaret Thatcher sunbathing on the beach in a bikini. Not surprisingly, this makes quite an impression on me, and for many years afterwards I can call up a vivid memory image of her lying on the beach. This surely remains true even if I am surreptitiously switched to Twin Earth and I happen to become well-acquainted with Twin-Thatcher. My image is still an image of Thatcher, even though I now believe it to be an image of Twin-Thatcher.²⁵ What matters in such a case as far as the particular object of the memory image is surely the historical cause of my percept, not whom I now causally interact with when I use the name ‘Thatcher’. So, here, it seems, privileged access does indeed fail: my memory image is not of the person whom I believe it to be.

     I am inclined to think that the externalist about propositional memory would do well simply to concede this point. Consider for a moment the case of seeing. For me to see Jones standing before me, Jones must really be standing before me and there must be the appropriate causal connection between the two of us. But it need not appear to me that Jones is present. Perhaps Jones is wearing a disguise so that it appears to me that someone else—Smith, say—is facing me. Likewise, the externalist can say for the case of memory. For me to have a (veridical) memory image of the earthly Thatcher sunbathing in a bikini, I must have seen her in a bikini and that perception must be appropriately causally connected to the image. But I need not now have a memory (in the broad sense that includes seeming memories) that Thatcher was sunbathing in a bikini. Given a suitable history of interactions on a suitable twin planet, my memory, according to the externalist, will be that Twin-Thatcher was doing the sunbathing.²⁶

     I am granting, then, that, where ‘of’ is so used that having a memory image of X entails that X exists, one’s current environmental or socio-environmental setting is irrelevant to what it is the image is of.²⁷ What matters is the past setting. However, one can certainly have memory images of things that never existed, for example, a flying saucer landing in one’s garden.²⁸ And where ‘of’ has a sense of this sort, it seems to me that the situation is, in important respects, parallel to the case of remembering-that. For in this sense of ‘of’, one surely has privileged access to what one’s memory image is of just as one has privileged access to the contents of one’s conscious propositional memories (allowing mismemories to count as memories). So, here the earlier arguments for externalism can still be brought to bear (with minor modifications).

     The externalist view of memory may remain puzzling. The externalist claims that in a wide range of cases, memory contents must answer to factors in the present environmental or socio-environmental setting. That may seem difficult to grasp. What sorts of representation could memory deploy that would render this position unproblematic?

     One representation that we have seen will not do the job is the photograph. But another that will is the symbol-structure, be it a sentence, a description, or a symbol-filled array. If memory consists in writing down and storing an inner sentence (or other symbol structure) which is subsequently retrieved, as is the case with conventional computer architectures, then the externalist thesis is that in certain cases the content of that sentence must change with an appropriate change or set of changes in the external setting, just as happens with the corresponding public sentences. No new source of puzzlement here.

     Suppose next that memory is viewed connectionistically. On this approach, at least to the extent that it is not merely an implementation of the classical, computational view, there are no stored representations of any sort in memory. Memory is not a storehouse or a library. Insofar as there is any information in the system when it is not being actively used, it is in the weights or strengths of connections between nodes. In a sense, on the connectionist account, information that is not being used is only present in the system potentially. This being so, when we remember something, we create the appropriate representation at the time in response to the stimulus (internal or external) in virtue of the weights that are already present.²⁹ We do not retrieve the representation from storage and operate upon it in the central processing unit, as we do on the classical, computational theory.

     On this approach to memory, the claim that memory-contents must answer to current socio-environmental factors again presents no special perplexity. Since it is now the case that the representations with such contents do not exist until the time of recollection, there are no contents that attach to the representations before they are retrieved, and hence there can be no question of the representations now having the contents they used to have in storage. So, if content-externalism is true anywhere, it should be true here.

     In this section, I have discussed a number of possible criticisms of the externalist view of memory. I have argued that none of them should give the externalist any cause for real concern. Given the plausibility of the case for memory externalism, the onus now lies with its opponents to show that there is some serious difficulty I have overlooked.³⁰

Michael Tye
Temple University and King’s College London

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