[Untitled] Reviewed Work(s): Thought Experiments. by Roy A. Sorensen Michael Slote Noûs, Vol. 28, No. 4. (Dec., 1994), pp. 526-533. Stable URL: http://links.jstor.org/sici?sici=0029-4624%28199412%2928%3A4%3C526%3ATE%3E2.0.CO%3B2-W Noûs is currently published by Blackwell Publishing.
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Roy A. Sorensen's Thought Experiments. NY and Oxford: Oxford University Press, 1992. MICHAELSLOTE
University of Maryland
Thought Experiments is a timely, lively book with a great deal to say about an important topic. Sorensen wants to offer a general account of thought experiments both in science and in philosophy, and his general strategy is to argue for and highlight the continuities and similarities between philosophical and scientific thought experiments. Because he thinks philosophy itself is continuous with science, Sorensen believes it is possible "to understand philosophical thought experiments by concentrating on their resemblance to scientific relatives (dustjacket)." But scientific and other thought experiments are themselves in turn to be understood in terms of (as limiting cases of) ordinary experiments, and the inference drawn is that scepticism about thought experiments is generally unwarranted. There are dangers in thought experiment both in philosophy and in science that Sorensen, in a fascinating final chapter, is at pains to enumerate and classify, but the effective conclusion of Thought Experiments is that naturalistic post-Quinean philosophers should be less sceptical about a priori philosophical methods than they have been told to be and typically are. A priori thought can itself receive a justification in empirical terms, and so although the practice, for instance, of thinking of imaginary counterexamples is less discrete from science than the advocates of philosophical analysis have usually imagined, scientific disciplines like psychology and evolutionary theory (and Thought Experiments makes considerable and interesting use of the latter) actually support the practice of pure philosophical analysis to a substantial degree. Sorensen, then, is not content with the justifications for thought experiment in philosophy that philosophers themselves have given and insists on (the need for) giving empirical justifications and even foundations for practices and forms of reasoning that philosophers have imagined were in some sense self-certifying or reasonable a priori. The philosophical examples Thought E.rperirnents concentrates on are frequently ethical (the scientific examples are frequently culled from physics). Sorensen regards the attempt to refute ethical theories, for example, by citing their presumably unacceptable implications for some logically possible case(s) or situation(s) as a use of thought experiment, and he doesn't make much of the distinction between such attempted refutations of ethical theories and thought-experimental arguments against one or another philosophical analysis of terms or concepts that also rely on putative counterexamples. But this leads him, I think, to misunderstand or at least misdescribe the character of ethical theories like Kantianism and utilitarianism. He says, for example, that utilitarians "define 'right' as the maximization of goodness.. ." (p. 235; see also similar remarks on p. 279, where Sorensen seems to blur the distinction between non-analytic, but totally general ethical theories like utilitarianism and the more limited generalizations of applied ethics). But post Rawls, most of us think of utilitarian act-consequentialism as an ethical theory, not a reportive or stipulative definition, and similarly for other ethical views. If we are to take Quineanism seriously in the way Sorenson so clearly does, we are no more justified in thinking of ethical theories as mere definitions than such an attitude would be justified in regard to
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quantum physics or economics. 1was a little surprised too when, in the course of the same discussion, Sorenson attributes to the (presumably) act-utilitarian the idea that we mistakenly think the actlomission distinction is morally relevant because it "covaries with factors that are relevant: intent, motive, certainty of result.. . ." (p. 235) What kind of actutilitarianism thinks motives are relevant to moral evaluation in a way that the actiomission (i. e . , cornmissionlomission) distinction isn't? There turn out, more generally, to be problems about some of the particular ways in which Sorensen defends his picture of thought experiments, especially in the area of ethics, but before examining some of these difficulties, I would like to give the reader of this review a taste of some of the liveliness of Thought E.rperirnents. The book abounds with delightful and instructive examples especially from the history of science, and at least some of these deserve to be mentioned in a review. Here is Sorensen's description of one of Galileo's uses of thought experiment: "Galileo's fascination with pendulums led him to design an inclined plane that demonstrates the law of equal heights. Just as the pendulum's bob recovers its original height as it swings from its top-left point to its top-right, a ball rolled along a double inclined plane will recover its original height.. . . Of course, Galileo realized that the ball's track was not perfectly smooth and that air had to be pushed aside by the ball. In real life the ball does not quite reach its original height because some of its energy is spend in the good fight against friction and air resistance. The law of equal heights only directly applies to an idealized counterpart of the physical setup.. . . His line of inquiry brings us a more dramatic kind of thought experiment in which we are doing more than stipulating away nuisance factors. Galileo asks us to suppose that one side of the plane is progressively lengthened, so that the ball must travel farther and farther to regain its original height.. . . In the limiting case of infinite lengthening, the ball never returns to its original height. Since the law of equal heights says the ball must continue until it does regain its original height, it follows that the ball will continue forever in a straight line. This thought experiment turned the theory of motion upside-down.. . . [Alfter Galileo's thought experiment, continued movement seemed natural and slowing required explanation." (pp. 8f.) This is a beautiful example of the power of thought experiment. And here is another that Sorensen describes for us: "Consider a problem frequently discussed by Gestalt psychologists. A monk begins a walk up a mountain Monday morning and reaches the summit in the late afternoon.. . . Tuesday morning he begins the walk down the same path and reaches the foot of the mountain in the early afternoon. Is there any place he occupied at the same time on each day? Although most people initially answer 'Probably not', a mental picture quickly shows that the the correct answer is 'Necessarily so'. Superimpose the scene of Tuesday journey on the Monday journey. Since the Monday monk going up the mountain must meet the Tuesday monk going down, there must be a place that was occupied at the same time of day." (p. 100) Sorensen also makes the case that thought experiments when suitably packaged can get
around intellectual defenses and undercut cherished beliefs in a way that a more frontal assault would fail to accomplish. He points out: "Philosophy teachers sometimes use a variant of John Wisdom's parable of the gardener this way. Suppose Theodore and Atwell come upon an old garden and are surprised to see that some of the original flowers flourish among the weeds. Theodore infers that there must be a gardener who tends the flowers while no one is looking. Atwell disagrees. So they camp out and carefully watch for a secret gardener. After none is detected, Theodore concludes that the gardener must be invisible. So they erect a glass dome around the garden. The flowers still flourish but no one breaks the glass. Theodore concludes that the gardener is incorporeal. More precautions just lead Theordore to infer that the gardener is completely indetectible to scientific testing. But Theodore still claims to know that 'The gardener cares'. ...Is Theodore rational? Students castigate Theodore on the grounds that his belief has degenerated into an unverifiable dogma. Then the teacher queries: 'What is the difference between Theodore's belief and a theist's?' Many of the students who confidently dismissed Theodore are themselves theists and so are startled by the similarity-more startled than they would have been had they been filtering the analogy through their intellectual defenses." (pp. 101f.) And one final example where, as Sorensen points out, the use of extreme examples can aid in the formulation of a counterexample: A flight from New York to San Francisco takes longer than the return trip because the North American continent has prevailing westerly winds. Do the passengers save as much time returning as they lost going? To see that they gain less than they lost, suppose that the wind is moving at 499 miles per hour while the plane only travels 500 miles per hour. Since the plane only nets 1 mile per hour, the trip to San Francisco will take a few months. The return flight will net 999 miles per hour and so take only a few hours. Nevertheless, the saving is swamped by the loss. The positive and negative effects of the wind look like they cancel out because we fail to consider how long the force works on the plane. Equal forces cancel out only when applied equally. The outlandish scenario has the advantage of being a flaming counterexample. Less extreme cases would not highlight the temporal element with the same intensity." (p. 104.) There are many other lovely examples of thought experiments mentioned by Sorensen in the course of his book, but the above must suffice for this review. It is time to look closer at some of his philosophical claims about the nature of thought experiment and the arguments and illustrations he uses to support them. Sorensen's approach is rather eclectic and pluralistic, rather than offering some grand design or unified theory. He discusses, for example, many models of "armchair inquiry" and tells us they all contain some truth. (p. 109) He says that thought experiments are (all) experiments, but he also claims they are (all) paradoxes and stories as well. (p. 6) However, Sorensen also allows himself a methodology that regiments all thought experiments into sets of individually plausible but jointly inconsistent propositions. The unity achieved in this way struck this reader as rather confining and unilluminating; sometimes it seemed even to detract from Sorensen's
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particular insights. And so it seems appropriate, in the light of the general success of Sorensen's typically rather catholic and piecemeal approach, that we take a look at some of the things Sorensen has to say about particular cases. Much of what he tells us is in fact quite illuminating. For example, Sorensen thinks it important to distinguish real experiments on (our own) mental states from thought experiments, a distinction most of us are probably unaware of. Thus consider the claim that bclicf is voluntary, that we literally decide what to believe. If such a thesis is met with the challenge "try to believe there is a jellyfish on your head," failure to form that particular belief is evidence that belief is involuntary. But, as Sorenson points out, that evidence is obtained by executing a real psychological experiment, not a thought experiment. I think he is right about this, but I don't think I at least would have known how to make the distinction in question in the absence of a nice example of the sort he gives us. Sorensen also mentions some interesting ways in which luck can play a role in ordinary experiments that it lacks in thought experiment. Thus "[iln 1825 Jean Daniel Colladon performed an experiment that probably achieved his goal of producing electricity by magnetism-but he did not notice. To ensure that his powerful magnet would not affect his galvanometer, he placed the galvanometer in another room. This necessitated a timeconsuming walk between rooms to check for an effect. Since the effect was instantaneous and fleeting, Colladon was always too late to see it." (p. 242) Sorensen says that thought experiments lack any "execution element" that can be subject to luck in this way, and I tend to agree-though I do wonder whether fatigue couldn't make one less attentive to conceptual nuances and affect the "outcome" of a conceptual thought experiment. This form of bad luck seems somewhat analogous to the kind mentioned in connection with Colladon. Because Sorensen is so attentive to detail and nuance and so genuinely pluralistic, I think the best place to take issue with him is, as I suggested above, in regard to his treatment of particular examples and smallish issues. All too often, I found, rather large and controversial philosophical assumptions are made in the course of dealing with rather minor topics or issues, and in some way this practice runs counter to the more piecemeal and empirical approach that runs through the book. As an ethicist, I was often struck by his use, without defense and without any indication of the need for defense, of metaethical and ethics-theoretic assumptions that to this reader at least seemed less than plausible or at least less than obvious. But there are also a number of assumptions about epistemology and the philosophy of language that struck me in similar fashion, and let me begin with these latter before going on to home territory. For example, there is Sorensen's frequent appeal to the authority of the principle of charity in order to establish points of interpretation or substance (see, e. g . , pp. 72, 134, 275). The principle of charity has come under attack in recent years in part as a result of experiments by psychologists like Nisbett and Ross that seem to show that most people are irrational in the inferences they are prepared to make. And although he does not cite them by name, Sorensen himself makes reference to the kinds of experiments just alluded to, when he says: "there is a a gloomy trend in the psychology of reasoning that suggests that human beings are surprisingly susceptible to fallacies (p. 85)." Why, then, does he find the principle of charity so authoritative? One would like to know or at least to have Sorensen indicate that the principle of charity has come (increasingly?) under fire in recent years and is therefore not perhaps absolutely to be relied upon. He also makes a particular application of the principle of charity that strikes me, again, as too quick, though in the end and after argument it might be possible to vindicate it.
Sorensen assumes (pp. 72f. and elsewhere) that we should minimize the inconsistencies we attribute to speakers or thinkers. The hypothesis of inconsistency should only be used as a last resort-indeed, he goes on to say, "we are never entitled to stoop that low." Now in the course of his discussion, Sorensen makes reference to our unwillingness to posit belief in "obvious contradictions," but one immediately then wants to know why he thinks it so unthinkable to posit belief in unobvious or subtle contradictions, and we are never told. Moreover, if the principle of charity is to be regarded as the source of unwillingness to posit inconsistent beliefs, then it is being assumed that it is irrational to have an inconsistent belief set, and such an assumption seems very much in need of defense. Of course, there is a literature about this, the issue is vexed and difficult-but then Sorensen could have said something about that literature or done something to make it clear that his own position about contradictions is far from decisively established. Consider, for example, the paradox of the preface, where someone is supposed to believe everything she writes in a book but also believes-what she writes in the preface-that there is error somewhere in her book. It is far from obvious that such a person is being irrational in or about her beliefs even if she knows that they form an inconsistent set and continues to hold them. What is she supposed to do instead, once she finds out she believes an inconsistent set? Which belief or beliefs is she supposed to drop? And if one says, she must drop something somewhere, for after all she now knows her beliefs to be inconsistent, I think I would want to know why it cannot in such a case as this be rational to believe each and every one of a set of beliefs, even while knowing the set is inconsistent and therefore not believing the conjunction of those beliefs. And if such a thing can be rational, then even given the principle of charity, it is not right to say that the hypothesis of inconsistency must be resorted to last or never. This is clearly a topic that goes well beyond the range of Sorensen's book, this review, and my own expertise, but I mention it as an example of what seems to me to be an overconfidence about certain controversial assumptions that one finds in Thought E.xperiments. Moreover, and let me say this now for later as well, it is not at all clear to me that Sorensen couldn't make most of his main points in the book without invoking some of the controversial views he inserts into the discussion in so many places. So I am complaining more about the way Sorensen carries out his task than about its ultimate viability, but the importation of so many controversial assumptions does make the book less effective as it now stands than it might otherwise be-it adds too much to distract the reader from its main purposes. Let me mention just one other place, outside of ethics, where it seems to me he makes things seem simpler than they really are. In discussing Berkeley's argument for idealism based on the putative impossibility of imagining an unperceived object, Sorensen distinguishes betweeen ''external" and "internal" supposition. There is a difference, he says, "between a supposition that you are following a procedure and following a procedure of supposition." (P. 203) And this difference is supposed to help us see the fallacy in Berkeley's argument for idealism. But even armed with this distinction, Sorensen ends up just asserting and reasserting the fallaciousness 'of Berkeley's argument. He says: "for there is a difference between supposing you are perceiving and just supposing.. . . It is one thing to imagine a tree in an uninhabited forest and another to imagine myself discreetly viewing a tree in an otherwise uninhabited forest." (P. 203) This way of proceeding doesn't do real justice to the force of Berkeley's argument. Of course, we don't want to believe its conclusion and feel there has to be a catch somewhere. But it seemed to me that
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Sorensen was far from pointing out where the problem really lies with Berkeley's argument and that itself is not an easy thing to do. A good deal of work has been done on this topic, and it is no part of my brief to enter into that discussion. But let me just mention one (for me) salient fact about Berkeley's argument. It trades on what seems to me to be a quite interesting fact about imagination: the fact (at least this seems to hold in my own case) that when we are asked to imagine an unperceived tree we perform or can perform what seems to be the very same act as we might perform if asked to imagine ourselves perceiving a tree. I think Berkeley's argument gains sustenance from this item of psychology, but Sorensen never really comes to grips with this aspect of the issue, and his discussion of the topic, despite the quite interesting new nomenclature, seemed not to get to the heart of the matter. But let me now turn to ethics and examples from ethics, to which, by his own description, Roy Sorensen has devoted a good portion of his thinking about thought experiments. Yet early on (p. 12) he describes ethics as well as aesthetics as "backwoods subfields" of philosophy, and a reader in either of these fields may feel cause to wony. And the worries increase as, time and again, Sorensen makes claims about or in ethics or related areas that seem either overconfident or misinformed. Above, I briefly mentioned some problems in Sorensen's characterization of utilitarianism, but I should mention that there are also problems in his description of social contract theory. On page 258, for example, he complains that force of habit can lead even seasoned thought experimenters to overstipulate, and as an instance of this he mentions the way in which "social contract theorists dispose of worries about stupidity and ignorance by assuming that the signers of the contract are perfectly rational and well informed." Citing Thomas Jefferson's opinion, Sorensen claims that such "saints" would have no need for government, or thus for any contract. But this is much too quick. We need to be told why rational and well- informed people would have no need for government-the claim just doesn't seem at all plausible, and it is effectively treated as such by Rawls, Gauthier, and other contemporary contract theorists. How, in other words, does knowledge and the kind of (relatively) self-interested rationality posited in typical contract theories make government unnecessary? Presumably, even beings with strong and univocal moral motivation need government, and I just don't understand what point Sorensen is trying to make here. Then (to go back again to page 12), there is Sorensen's statement that "evaluative thought experiments appear hopelessly marooned by the fact-value gap." But the very existence of a fact-value gap is questioned by many philosophers nowadays, as a result of earlier work by Foot, Anscombe, Geach, and others. As prescriptivism and emotive meaning have come under fire from neo-naturalists, it has appeared very difficult to draw even a vague line between fact and value and to many the two categories are simply inextricably linked or interfused. (Sorensen tends to treat the fact-value distinction as the same as the is-ought distinction, but this too, in the light of work by Wiggins, Foot and others is highly questionable.) Moreover, given Sorensen's own gradualism and Quinean leanings, it is somewhat surprising that he should so automatically place reliance on the existence of a fact-value distinction. And I don't, see why he couldn't have altogether avoided committing himself on this issue, while still accomplishing what he needs to in regard to thought experiments. At a somewhat later point in the book, I think a similar oversimplification of difficult issues occurs in connection with the problem of free will. Sorensen claims:
"[An] equivocation of standards is evident in dialogues with determinists. You say that you could have chosen to read a different book? But didn't your choice issue from a particular set of beliefs and desires? Aren't those psychological properties a product of your genetic makeup plus your upbringing? Just when did your future become unfixed, open, free? The determinist traps his interlocutor by subtly changing the question. We begin with issue of whether [an] alternate book selection is consistent with a loose set of laws and initial conditions and wind up with the question of whether the selection was consistent with a highly specific set of laws and initial conditions. By supersaturating the context with detail, one makes the event inevitable." (p. 150) This passage contains a diagnosis of the free-will debate that fits in well with Sorensen's views about vagueness and ambiguity but doesn't sit very well with the way most contemporary work on freedom and determinism sees what is involved in that debate. Why assume that the determinist (by which, I take it, Sorensen means the incompatibilist) changes the question? Why assume the compatibilist assumes or has to assume "loose" laws and conditions in order to be on firm intellectual ground? By proceeding as he does, Sorensen, far from offering an uncontroversial analysis of the free-will debate, actually takes sides in it. He simply assumes, at the end of the above quotation, that if laws and conditions are fixed, then an event is inevitable in the sense relevant to free will. This is precisely what many contemporary compatibilists (myself among them) dispute, claiming that an ordinary or reasonable understanding of modal notions in fact allows slippage between strict determinism and unfreedom. But one would never guess this possibility existed for contemporary discussions of freedom from the way Sorensen diagnoses the issue. And let me by way of final example briefly mention what I take to be another oversimplification in regard to the issue of God's omnipotence. In his chapter on "The Logical Structure of Thought Experiments," Sorensen presents a quite interesting discussion of the way claims of possibility and claims of necessity can be refuted by thought experiment, introducing new terminology and argumentation structures that nicely illustrate these issues. But for me, at least, he mars the presentation somewhat by making quick and unjustified assumptions in the course of illustrating his views. In discussing how the famous paradox of the stone relates to his theory of "possibility refuters," he says: "If God exists, then it is possible for an omnipotent being to exist. If there were an omnipotent being and he tried to make a stone so big that he himself could not lift it, then he would succeed (because he can do anything) and not succeed (because success implies a contradiction). But no one can both succeed and not succeed at a task." Again, this goes too fast, and some of the recent literature of the philosophy of religion (especially work by Swinburne) would certainly agree. Just to take the most obvious point, it doesn't follow from the fact that God is omnipotent, that he is essentially omnipotent, at least it isn't obvious that this follows. And if God isn't essentially omnipotent, there is no contradiction of the sort Sorensen thinks there is, in the supposition that an omnipotent God has made or will make a stone so big (or heavy) that he cannot (having made it) lift it. The act of making the stone could involve or be conjoined with a shuffling off of omnipotence, and perhaps it is essential to omnipotence that one be able to get rid of
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one's omnipotence, so that omnipotence is essentially an accidental property of any beings who might possess it. I certainly wouldn't want to claim that such assumptions obviate all paradox in regard to omnipotence and the making of stones too large or heavy to lift, but Sorensen's presentation makes it too easy to avoid paradox, and so the attempt to illustrate issues concerning possibility refuters is marred at least in detail. But some of the objections I have been making are in fact mainly a matter of detail-and one might also say of philosophical style. Sorensen may be less careful or cautious about certain philosophical claims pertaining to questions other than the nature of thought experiments, because he is really more interested in the latter. But if he proceeds in that fashion, he will bother some philosophers withdifferent views and potentially mislead non-philosophical readers. The book's blurb says that "Thought Experiments is interesting and accessible to a wide audience of philosophically-minded scientists and scientifically-minded philosophers as well as psychologists, physicists, and historians of ideas." And I think the psychologists and others who are not trained in philosophy will be given afalse sense of security about which philosophical issues are settled from the way Sorensen treats many such issues. Also, there are times-though it is a good thing about this book that they are not too frequent-when the non- philosopher will encounter terms and problems she is given no basis for understanding. Just to give two striking examples, the language of thought is mentioned (pp. 97f.) without any real preparation or clarification, and the same thing happens in connection with relevance logic on page 121. But despite these problems of detail and execution, Thought Experiments can be recommended to any reader interested in its general topic. It is freshly written and reasoned, and although we don't end up with a unified grand theory of thought experiment, we are given many, many insights about the structure of argument by thought experiment and the relations between thought experiment and related intellectual phenomena.
Michael Williams' Unnatural Doubts. Cambridge: Blackwell, 1991. Skepticism and Foundationalism
ANTHONY BRUECKNER University of California, Santa Barbara 1. Introduction Michael Williams argues that skepticism about knowledge of the external world does not arise from plausible intuitive considerations about knowledge. Instead, he claims, skepticism depends on controversial theoretical doctrines which are foundationalist in character. In his earlier book, Groundless Belief, he criticized foundationalism and maintained that its When I first studied that book, it seemed to downfall induces the downfall of skeptici~m.~ me that Williams' way with skepticism was too quick. He focussed upon Ayer's formulation
