Against Norton's claim that all thought experiments can be reduced to explicit arguments, I defend Brown's position that certain thought experiments yield a priori knowledge. They do this, I argue, not by allowing us to perceive “Platonic universals” (Brown), even though they may contain non-propositional components that are epistemically indispensable, but by helping to identify certain tacit presuppositions or “natural interpretations” (Feyerabend's term) that lead to a contradiction when the phenomenon is described in terms of them, and by suggesting a (...) new natural interpretation in terms of which the phenomenon can be redescribed free of contradiction. (shrink)

My theme is thought experiment in natural science, and its relation to real experiment. I shall defend the thesis that thought experiments that do not lead to theorizing and to a real experiment are generally of much less value that those that do so. To illustrate this thesis I refer to three examples, from three very different periods, and with three very different kinds of status. The first is the classic thought experiment in which Galileo imagined that he had, by (...) pure thought, demolished Aristoteles' dogma that heavier bodies fall more quickly than light ones. I will show that he was mistaken. The second is the Einstein-Podolsky-Rosen paper purporting to show that quantum mechanics must be incomplete in its domain of application. This thought experiment is a very good one, not because its conclusions are correct, but precisely because it was fruitful, leading to theory and, above all, to a real experiment. Finally I discuss the modern string theory of everything, which, while it is regarded as a physical theory by its instigators, shares some properties of the least successful sort of thought experiment. (shrink)

We have never entirely agreed with Daniel Cohnitz on the status and rôle of thought experiments. Several years ago, enjoying a splendid lunch together in the city of Ghent, we cheerfully agreed to disagree on the matter; and now that Cohnitz has published his considered opinion of our views, we are glad that we have the opportunity to write a rejoinder and to explicate some of our disagreements. We choose not to deal here with all the issues that Cohnitz raises, (...) but rather to restrict ourselves to three specific points. (shrink)

A characteristic of contemporary analytic philosophy is its ample use of thought experiments. We formulate two features that can lead one to suspect that a given thought experiment is a poor one. Although these features are especially in evidence within the philosophy of mind, they can, surprisingly enough, also be discerned in some celebrated scientific thought experiments. Yet in the latter case the consequences appear to be less disastrous. We conclude that the use of thought experiments is more successful in (...) science than in philosophy. (shrink)

Marya Schechtman's The Constitution of Selves presented an impressive attempt to persuade those working on personal identity to give up mainstream positions and take on a narrative view instead. More recently, she has presented new arguments with a closely related aim. She attempts to convince us to give up the view of identity as a matter of psychological continuity, using Derek Parfit's story of the “Nineteenth Century Russian” as a central example in making the case against Parfit's own view, and (...) offers a form of narrative theory as a way out of the problem. In this paper I consider this new case, and argue that we should not be persuaded towards the narrative. (shrink)

: An examination of two thought experiments in contemporary physics reveals that the same thought experiment can be reanalyzed from the perspective of different and incompatible theories. This fact undermines those accounts of thought experiments that claim their justificatory power comes from their ability to reveal the laws of nature. While thought experiments do play a genuine evaluative role in science, they do so by testing the nonempirical virtues of a theory, such as consistency and explanatory power. I conclude that, (...) while their interpretation presupposes a whole set of background theories and putative laws, thought experiments nonetheless can evolve and be retooled for different theories and ends. (shrink)

The literature on thought experiments has been mainly concernedwith thought experiments that are directed at a theory, be it in aconstructive or a destructive manner. This has led somephilosophers to argue that all thought experiments can beformulated as arguments. The aim of this paper is to drawattention to a type of thought experiment that is not directed ata theory, but fulfills a specific function within a theory. Suchthought experiments are referred to as functional thoughtexperiments, and they are routinely used in (...) applied statistics. An example is given from frequentist statistics, where a thoughtexperiment is required to establish the probability space. It isconcluded that (a) not all thought experiments can be formulated asarguments, and (b) the role of thought experiments is more generaland more important to scientific reasoning than has previouslybeen recognized. (shrink)

I begin with an explication of "thought experiment". I then clarify the role that intuitions play in thought experiments by addressing two important issues: (1) the informativeness of thought experiments and (2) the legitimacy of the method of thought experiments in philosophy and the natural sciences. I defend a naturalistic account of intuitions that provides a plausible explanation of the informativeness of thought experiments, which, in turn, allows thought experiments to be reconstructed as arguments. I also specify criteria for distinguishing (...) bad "intuition pumps" from legitimate thought experiments. These criteria help us to avoid being seduced by the dangerous suggestive power of misleading intuitions. (shrink)

In this paper I argue that (at least many) philosophical thought experiments are unreliable. But I argue that this notion of unreliability has to be understood relative to the goal of thought experiments as knowledge producing. And relative to that goal many thought experiments in science are just as unreliable. But in fact thought experiments in science play a varied role and I will suggest that knowledge production is a goal only under quite limited circumstances. I defend the view that (...) these circumstances can (sometimes) arise in philosophy as well. (shrink)

In their recent paper, "When are thought experiments poor ones?" (Peijnenburg/Atkinson 2003), Jeanne Peijnenburg and David Atkinson present an argument to the conclusion that most, if not all, philosophical thought experiments are "poor" ones with "disastrous consequences" and that they share this property with some (but not all) scientific thought experiments. The moral they draw is that the use of thought experiments in science is generally more successful than in philosophy (of mind). In this comment I shall briefly try to (...) show that Peijnenburg's and Atkinson's view on thought experiments as it is presented in Peijnenburg/Atkinson 2003, but also in Atkinson/Peijnenburg [forthcoming], and Atkinson 2003, is based on an misleading characterization of both, the dialectical situation in philosophy as well as the history of physics. By giving an adequate account of what the discussion in contemporary philosophy is about, we will arrive at a quite different evaluation of philosophical thought experiments. (shrink)

The ontological argument is one of the most intriguing lines of reasoning in Western thought. Leaving behind debates over the proper relation between science and religion, it makes a simple move from conceptual analysis to existence in order to prove the existence of god. The ontological argument will be reviewed against the background of the contemporary debate on thought experiments. Assuming that the ontological argument fails as a philosophical proof, I will argue that its move from concept to existence might (...) best be understood as a thought experiment of revealed theology (a theology based on revelation – unlike philosophical theology/natural theology). Viewed from this perspective it makes sense that Anselm of Canterbury offered his versions of the ontological argument in the form of a prayer, which, presupposing the existence of god, seems to run counter to a proof of god's existence. (shrink)

It is a commonplace that contemplation of an imaginary particular may have cognitive and motivational effects that differ from those evoked by an abstract description of an otherwise similar state of affairs. In his Treatise on Human Nature, Hume ([1739] 1978) writes forcefully of this.

The capacity to represent things to ourselves as possible plays a crucial role both in everyday thinking and in philosophical reasoning; this volume offers much-needed philosophical illumination of conceivability, possibility, and the relations between them.

To what extent and how is conceivability a guide to possibility? This essay explores general philosophical issues raised by this question, and critically surveys responses to it by Descartes, Hume, Kripke and "two-dimensionalists.".

Contemplating imaginary scenarios that evoke certain sorts of quasi‐sensory intuitions may bring us to new beliefs about contingent features of the natural world. These beliefs may be produced quasi‐observationally; the presence of a mental image may play a crucial cognitive role in the formation of the belief in question. And this albeit fallible quasi‐observational belief‐forming mechanism may, in certain contexts, be sufficiently reliable to count as a source of justification. This sheds light on the central puzzle surrounding scientific thought experiment, (...) which is how contemplation of an imaginary scenario can lead to new knowledge about contingent features of the natural world. (shrink)

Through careful analysis of a specific example, Parfit’s ‘fission argument’ for the unimportance of personal identity, I argue that our judgements concerning imaginary scenarios are likely to be unreliable when the scenarios involve disruptions of certain contingent correlations. Parfit’s argument depends on our hypothesizing away a number of facts which play a central role in our understanding and employment of the very concept under investigation; as a result, it fails to establish what Parfit claims, namely, that identity is not what (...) matters. I argue that Parfit’s conclusion can be blocked without denying that he has presented an imaginary case where prudential concern would be rational in the absence of identity. My analysis depends on the recognition that the features that explain or justify a relation may be distinct from the features that underpin it as necessary conditions. (shrink)

By carefully examining one of the most famous thought experiments in the history of science—that by which Galileo is said to have refuted the Aristotelian theory that heavier bodies fall faster than lighter ones—I attempt to show that thought experiments play a distinctive role in scientific inquiry. Reasoning about particular entities within the context of an imaginary scenario can lead to rationally justified concluusions that—given the same initial information—would not be rationally justifiable on the basis of a straightforward argument.

Retributivist arguments often employ thought experiments meant to elicit various responses from us - materials with which, it is hoped, compelling arguments for punishment can be constructed. Many think that these experiments help make a prima facie case for punishment, that they highlight reasons that speak unequivocally, if not decisively, in punishment's favor. Retributivist use of these experiments has gone insufficiently challenged. I plan to turn the tables on the retributivist. These experiments do not highlight reasons for punishment. In fact, (...) examination of these experiments and arguments that have employed them can help emphasize the strength of Abolitionism, the view that punishment is unjustified. I will show how these experiments have been and can be mishandled and what insights can be taken from them once we identify the errors that have plagued their use. Retributivist arguments employing these experiments suffer from a variety of problems. They rely on dubious and ambiguous claims about the nature and content of the responses elicited by the experiments, misconstrue the moral import of some of the responses, and insufficiently question mistaken assumptions that influence the responses. (shrink)

Preface: This volume originated in a conference on "The Place of Thought Experiments in Science and Philosophy" which was organized by us and held at the Center for Philosophy of Science at the University of Pittsburgh, April 18-20, 1986. The idea behind this conference was to encourage philosophers and scientists to talk to each other about the role of thought experiments in their various disciplines. These papers were either written for the conference, or were written after it by commentators and (...) other participants.... We hope that this volume will be of use to other philosophers and scientists who are interested in thought experiments, as well as inspire more work in this area. (shrink)

I criticize Timothy Williamson’s characterization of thought experiments on which the central judgments are judgments of contingent counterfactuals. The fragility of these counterfactuals makes them too easily false, and too difficult to know.

Forthcoming in Philosophical Studies. Penultimate draft; please refer to published version. Abstract. What sorts of things are the intuitions generated via thought experiment? Timothy Williamson has responded to naturalistic skeptics by arguing that thought-experiment intuitions are judgments of ordinary counterfactuals. On this view, the intuition is naturalistically innocuous, but it has a contingent content and could be known at best a posteriori. We suggest an alternative to Williamson’s account, according to which we apprehend thought-experiment intuitions through our grasp on truth (...) in fiction. On our view, intuitions like the Gettier intuition are necessarily true and knowable a priori. Our view, like Williamson’s, avoids naturalistic skepticism. (shrink)

The scales across which physical properties exist are vast and subtle in their effects on particular systems placed locally on such scales. For example, human experiential access is restricted only to partial segments of the mass density, size, and temperature scales of the universe. I argue that philosophers must learn to appreciate better the effects of physical scales. Specifically, thought experiments in philosophy should be more sensitive to physical scale effects, because the conclusion of a thought experiment may be undermined (...) by unintentionally ignored scale effects, and the changes required to obtain the foreground state of affairs in a thought experiment might require unacknowledged scale-spanning changes to the contextual background. I discuss four philosophical thought experiments: Putnam's Twin Earth and Brain in a Vat, Searle's Chinese Room, and Chalmers's Zombies Without Qualia. I close by briefly defending the greater interest and importance of physical possibility over logical possibility. (shrink)

The main concern of this paper is to show that understanding mental variation may prove to be relevant to inquiry into thought experiments. First, I examine why Ernst Mach considered the ability to vary the contents of one's thoughts the principal requirement for thought experimentation. Second, I illustrate the wide applicability of mental variation in thought experiments. Third, I suggest, following Kathleen Wilkes, that variation is frequently employed in “realistic” thought experiments.

Since there isn't a computer that seems conscious at this time, the idea of machine consciousness is supported by thought experiments. Here's one old chestnut: "What if you replaced your neurons one by one with neuron sized and shaped substitutes made of silicon chips that perfectly mimicked the chemical and electric functions of the originals? If you just replaced one single neuron, surely you'd feel the same. As you proceed, as more and more neurons are replaced, you'd stay conscious. Why (...) wouldn't you still be conscious at the end of the process, when you'd reside in a brain shaped glob of silicon? And why couldn't the resulting replacement brain have been manufactured by some other means?". (shrink)

There has been a movement recently to bring to bear on the conduct of philosophical thought experiments (henceforth “thought experiments”)1 the empirical techniques of the social sciences, that is, to treat their conduct as in the nature of an anthropological investigation into the application conditions of the concepts of a group of subjects. This is to take a third person, in contrast to the traditional first person, approach to conceptual analysis. This has taken the form of conducting surveys about scenarios (...) used in thought experiments.2 It has been called “experimental philosophy” by its practitioners and has been applied across a range of fields: the philosophy of language, the philosophy of action, the philosophy of mind, epistemology, and ethics.3 The results of these surveys have been used to support conclusions about the application conditions of particular concepts of interest in philosophy. They have also been used to support (and been motivated by) skeptical claims about the traditional approach to conceptual analysis. The.. (shrink)

Roy Sorensen advances an evolutionary explanation of our capacity for thought experiments which doubles as a naturalized epistemological justification. I argue Sorensens explanation fails to satisfy key elements of environmental-selectionist explanations and so fails to carry epistemic force. I then argue that even if Sorensen succeeds in showing the adaptive utility of our capacity, he still fails to establish its reliability and hence epistemic utility. I conclude Sorensens account comes to little more than a just-so story.

Thought experiment acquires evidential significance only on particular metaphysical assumptions. These include the thesis that science aims at uncovering "phenomena"universal and stable modes in which the world is articulatedand the thesis that phenomena are revealed imperfectly in actual occurrences. Only on these Platonically inspired assumptions does it make sense to bypass experience of actual occurrences and perform thought experiments. These assumptions are taken to hold in classical physics and other disciplines, but not in sciences that emphasize variety and contingency, such (...) as Aristotelian natural philosophy and some forms of historiography. This explains why thought experiments carry weight in the former but not the latter disciplines. (shrink)

Canadian Journal of Philosophy, 26, pp. 333-66. 1996.

Thought experiments in science are merely picturesque argumentation. I support this view in various ways, including the claim that it follows from the fact that thought experiments can err but can still be used reliably. The view is defended against alternatives proposed by my cosymposiasts.

Thought experiments are ordinary argumentation disguised in a vivid pictorial or narrative form. This account of their nature will allow me to show that empiricism has nothing to fear from thought experiments. They perform no epistemic magic. In so far as they tell us about the world, thought experiments draw upon what we already know of it, either explicitly or tacitly; they then transform that knowledge by disguised argumentation. They can do nothing more epistemically than can argumentation. I defend my (...) account of thought experiments in Section 3 by urging that the epistemic reach of thought experiments turns out to coincide with that of argumentation and that this coincidence is best explained by the simple view that thought experiments just are arguments. Thought experiments can err—-a fact to be displayed by the thought experiment - anti thought experiment pairs of Section 2. Nonetheless thought experiments can be used reliably and, I urge in Section 4., this is only possible if they are governed by some very generalized logic. I will suggest on evolutionary considerations that their logics are most likely the familiar logics of induction and deduction, recovering the view that thought experiment is argumentation. Finally in Section 5 I defend this argument based epistemology of thought experiments against competing accounts. I suggest that these other accounts can offer a viable epistemology only insofar as they already incorporate the notion that thought experimentation is governed by a logic, possibly of very generalized form. (shrink)

A characteristic of contemporary analytic philosophy is its ample use of thought experiments. We formulate two features that can lead one to suspect that a given thought experiment is a poor one. Although these features are especially in evidence within the philosophy of mind, they can, surprisingly enough, also be discerned in some celebrated scientific thought experiments. Yet in the latter case the consequences appear to be less disastrous. We conclude that the use of thought experiments is more successful in (...) science than in philosophy. (shrink)

Thought experiments are ubiquitous in science and especially prominent in domains in which experimental and observational evidence is scarce. One such domain is the causal analysis of singular events in history. A long‐standing tradition that goes back to Max Weber addresses the issue by means of ‘what‐if’ counterfactuals. In this paper I give a descriptive account of this widely used method and argue that historians following it examine difference makers rather than causes in the philosopher’s sense. While difference making is (...) neither necessary nor sufficient for causation, to establish difference makers is more consistent with the historians’ more ultimate purposes. †To contact the author, please write to: Department of Philosophy, Erasmus University, 3000 DR Rotterdam, The Netherlands; e‐mail: reiss@fwb.eur.nl. (shrink)

In this paper we propose to argue for two claims. The first is that a sizeable group of epistemological projects – a group which includes much of what has been done in epistemology in the analytic tradition – would be seriously undermined if one or more of a cluster of empirical hypotheses about epistemic intuitions turns out to be true. The basis for this claim will be set out in Section 2. The second claim is that, while the jury is (...) still out, there is now a substantial body of evidence suggesting that some of those empirical hypotheses are true. Much of this evidence derives from an ongoing series of experimental studies of epistemic intuitions that we have been conducting. A preliminary report on these studies will be presented in Section 3. In light of these studies, we think it is incumbent on those who pursue the epistemological projects in question to either explain why the truth of the hypotheses does not undermine their projects, or to say why, in light of the evidence we will present, they nonetheless assume that the hypotheses are false. In Section 4, which is devoted to Objections and Replies, we’ll consider some of the ways in which defenders of the projects we are criticizing might reply to our challenge. Our goal, in all of this, is not to offer a conclusive argument demonstrating that the epistemological projects we will be criticizing are untenable. Rather, our aim is to shift the burden of argument. (shrink)