's argumentation in favour of essential invariability of the fundamental laws of nature is critically examined. It is contended that within the realist framework Poincareé's arguments lose their apodictical force. In this sense the assumption of inconstancy of even the fundamental laws of nature is methodologically legitimate.

Ruben Berrios Queen’s University Belfast Anti-realism and Aesthetic Cognition Abstract At the core of the debate between scientific realism and anti-realism is the question of the relation between scientific theory and the world. The realist possesses a mimetic conception of the relation between theory and reality. For the realist, scientific theories represent reality. The anti-realist, in contrast, seeks to understand the relations between theory and world in non-mimetic terms. We will examine Cartwright’s simulacrum account of explanation in order to illuminate (...) the anti-realist position. Science consists of phenomenological and theoretical laws. The former are concerned with appearances, or those phenomena that can be directly observed; the latter involve the unobservable reality that is alleged to underlie appearances, and are capable only of indirect confirmation. Phenomenological laws are said to be descriptive, whilst theoretical laws are understood as explanatory. Cartwright is concerned with the theoretical. She claims that the standard realist account of the explanatory efficacy of theoretical laws is faulty. The explanatory power of theoretical laws consists in their ability to provide an explanation of physical phenomena. According to Cartwright, the realist claims that laws explain phenomena by providing an abstract description of them, in terms of their micro-structural features, that is alleged to be true. On this view, explanatory power is entirely dependent on descriptive adequacy. As phenomenological laws describe appearances, so theoretical laws describe the fundamental reality that governs appearances. Cartwright rejects the preceding view and in its place proposes a simulacrum account of explanation. According to Cartwright, the explanatory power of theoretical laws is related not to descriptive adequacy, but rather to the construction of adequate models. To explain a phenomenon is to construct a model which best or most adequately accommodates the phenomenon to a theory. The model will consist of various posited objects that serve to explain the phenomena in terms that are consistent with a set of theoretical laws. Cartwright claims that theoretical laws are true of, or describe, the objects of the model. The objects of the model, however, are not descriptive of reality. They are simulacra. They have, that is, the form or appearance of things, without possessing their substance or proper qualities. In light of the foregoing account we can summarise the distinction between scientific realism and anti-realism as follows. The realist claims that theoretical laws literally represent real objects. The anti-realist claims that laws represent objects of a model that are simulacra of reality. Anti-realism has an aesthetic dimension. The movement from realism to anti-realism is also the movement from the mimetic conception of the scientist as holding a mirror to nature to the constructionist view of the scientist as engaging with nature through invention. There is a lot of the artist in the anti-realist’s view of the scientist. This is true for Cartwright as well as, for example, Van Fraassen in his doctrine of constructive empiricism. It would appear, then, that the philosophy of science has absorbed some concepts that are ordinarily housed in aesthetics. And it has done so profitably. The aim of this paper is to reverse the direction of disciplinary influence. Can art, in relation to its status as a cognitive enterprise, be illuminated by scientific anti-realism? I will argue that it can. In an unexpected reference to the Nicomachean Ethics, Cartwright draws a suggestive parallel between theoretical laws and general moral principles, on the one hand, and physical phenomena and everyday moral conduct, on the other hand. If we add to this the claim that a central component of art’s value is cognitive, then we have the basic materials with which to flesh out a broadly anti-realist view of art. In the production of art, artists can construct models that mediate between everyday ethical phenomena and general ethical tendencies. These models reveal the ways in which there are implicit consistencies or inconsistencies, conflicts or congruences and so forth, between the phenomena and the tendencies. On this basis art can contribute to the reflective understanding of ethical life. This constitutes to a large degree art’s status as a cognitive enterprise. To apprehend art cognitively as artist or critic is to engage in aesthetic cognition. (shrink)

David Lewis’s ‘Humean Supervenience’ (henceforth ‘HS’) combines realism about laws, chances, and dispositions with a sparse ontology according to which everything supervenes on the overall spatiotemporal distribution of non-dispositional properties (Lewis 1986a, Philosophical papers: Volume II, pp. ix–xvii, New York: Oxford Univesity Press, 1994, Mind 103:473–490). HS faces a serious problem—a “big bad bug” (Lewis 1986a, p. xiv): it contradicts the Principal Principle, a seemingly obvious norm of rational credence. Two authors have tried to rescue Lewis’s ontology from the ‘big (...) bad bug’ (henceforth ‘the Bug’) by rejecting realism about laws, chances, and dispositions (Halpin 1994, Aust J Phil 72:317–338, 1998, Phil Sci 65:349–360; Ward 2005, Phil Sci 71:241–261). I will argue that this strategy cannot possibly work: it is the ontology, not the realist thesis, that lies at the root of the problem. (shrink)

I develop a metaphysical position that is both lawless and anti-Humean. The position is called realist lawlessness and contrasts with both Humean lawlessness and nomological realism – the claim that there are laws in nature. While the Humean view also allows no laws, realist lawlessness is not Humean because it accepts some necessary connections in nature between distinct properties. Realism about laws, on the other hand, faces a central dilemma. Either laws govern the behaviour of properties from the outside or (...) from the inside. If the former, an unacceptable quidditist view of properties follows. But no plausible account of laws within properties can be developed that permits a governing role specifically for laws. I conclude in favour of eliminativism about laws. At the conceptual core, the notion of a law in nature is misleading. It is suggestive of an otherwise static world in need of animation. (shrink)

A leaf falls to the ground, wafting lazily on the afternoon breeze. Clouds move across the sky, and birds sing. Are these events governed by universal laws of nature, laws that apply everywhere without exception, subsuming events such as the falling of the leaf, the movement of the clouds and the singing of the birds? Are such laws part of a small set of fundamental laws, or descended from such a set, which govern everything there is in the world?

There are few, perhaps no known, exact, true, general laws. Some of the work of generalization is carried by ceteris paribus generalizations. I suggest that many models continue such work in more complex form, with the idea of ceteris paribus conditions thought of as extended to more general conditions of application. I use the term regularity guide to refer collectively to cp‐generalizations and such regularity‐purveying models. Laws in the traditional sense can then be thought of as idealizations, which idealize away (...) from the conditions of application of regularity guides. If we keep clearly in mind the status of laws as such idealizations, problems surrounding traditional topics—such as lawlikeness, corresponding counterfactuals and modality—no longer look to be intractable. (shrink)

According to ‘regularity theories’ of causation, the obtaining of causal relations depends on no more than the obtaining of certain kinds of regularity. Regularity theorists are thus anti-realists about necessary connections in nature. Regularity theories of one form or another have constituted the dominant view in analytic Philosophy for a long time, but have recently come in for some robust criticism, notably from Galen Strawson. Strawson’s criticisms are natural criticisms to make, but have not so far provoked much response from (...) regularity theorists. The paper considers and rebuts Strawson’s objections. For example, Strawson claims that if there were no necessary connections in nature, we ought continually to find the regularity of the Universe surprising. I argue that the fact that the Universe is regular is something we take ourselves (fallibly) to know, and hence, in the light of this knowledge, its continued orderliness is not at all surprising. (shrink)

I argue for the claim that if Lewis’s regularity theory of laws were true, we could not know any positive law statement to be true. Premise 1: According to that theory, for any law statement true of the actual world, there is always a nearby world where the law statement is false (a world that differs with respect to one matter of particular fact). Premise 2: One cannot know a proposition to be true if it is false in a nearby (...) world (the epistemological safety principle). The conclusion that no law statement can be known to be true follows immediately from the two premises. (shrink)

Debates concerning the analysis of the concept of law of nature must address the following problem. On the one hand, our grasp of laws of nature is via our knowledge of their instances. And this seems not only an epistemological truth but also a semantic one. The concept of a law of nature must be explicated in terms of the things that instantiate the law. It is not simply that a piece of metal that conducts electricity is evidence for a (...) law that metals conduct electricity. It is also the case that to explicate what it is for there to be such a law requires, and requires little more than, alluding to the fact that the piece of metal conducting electricity is an instance of that law. This is the driving intuition behind regularity theories of laws — to understand the concept ‘law,’ as in ‘it is a law that metals conduct electricity’ one need only understand little more than what it is for something to be a metal and to conduct electricity and the concept of universal generalization. On this view a law just is a regularity (or some kind of regularity) among its instances. (shrink)

David Lewis’s ‘Humean Supervenience’ (henceforth ‘HS’) combines realism about laws, chances, and dispositions with a sparse ontology according to which everything supervenes on the overall spatiotemporal distribution of non-dispositional properties (Lewis 1986a, Philosophical papers: Volume II, pp. ix–xvii, New York: Oxford Univesity Press, 1994, Mind 103:473–490). HS faces a serious problem—a “big bad bug” (Lewis 1986a, p. xiv): it contradicts the Principal Principle, a seemingly obvious norm of rational credence. Two authors have tried to rescue Lewis’s ontology from the ‘big (...) bad bug’ (henceforth ‘the Bug’) by rejecting realism about laws, chances, and dispositions (Halpin 1994, Aust J Phil 72:317–338, 1998, Phil Sci 65:349–360; Ward 2005, Phil Sci 71:241–261). I will argue that this strategy cannot possibly work: it is the ontology, not the realist thesis, that lies at the root of the problem. (shrink)

Perhaps the most significant contemporary theory of lawhood is the Best System (/MRL) view on which laws are true generalizations that best systematize knowledge. Our question in this paper will be how best to formulate a theory of this kind. We’ll argue that an acceptable MRL should (i) avoid inter-system comparisons of simplicity, strength, and balance, (ii) make lawhood epistemically accessible, and (iii) allow for laws in the special sciences. Attention to these problems will bring into focus a useful menu (...) of novel MRL theories, some of which solve problems the original MRL theory could not. Hence we conceive of the paper as moving toward a better Best System theory of laws. (shrink)

The 'best-system' analysis of lawhood [Lewis 1994] faces the 'zero-fit problem': that many systems of laws say that the chance of history going actually as it goes--the degree to which the theory 'fits' the actual course of history--is zero. Neither an appeal to infinitesimal probabilities nor a patch using standard measure theory avoids the difficulty. But there is a way to avoid it: replace the notion of 'fit' with the notion of a world being typical with respect to a theory.

David Lewis[ii] has long defended an account of scientific law acceptable even to an empiricist with significant metaphysical scruples. On this account, the laws are defined to be the consequences of the best system for axiomitizing all occurrent fact. Here "best system" means the set of sentences which yields the best combination of strength of descriptive content[iii] with simplicity of exposition. And occurrent facts, the facts to be systematized, are roughly the particular facts about a localized space-time region that are (...) non-modal, non-dispositional, and non-causal. (shrink)

An acceptable empiricist account of laws of nature would havesignificant implications for a number of philosophical projects. For example, such an account may vitiate argumentsthat the fundamental constants of nature are divinelydesigned so that laws produce a life permittinguniverse. On an empiricist account, laws do not produce the universe but are designed by us to systematize theevents of a universe which does in fact contain life; so any ``fine tuning'' of natural law has a naturalistic explanation.But there are problems for (...) the empiricist project. This paper develops a ``perspectival'' version of the Humean bestsystem approach and argues that this version solves the standard problems faced by the empiricist project.Furthermore, the paper argues, this version is best able to answer the proponents of divine design while leaving scientificlaw a suitably objective matter.[I]t is possible tocondense the enormous mass of results to a large extent – that is to find laws which summarize ...Richard Feynman (1963)It has become fashionable in some circles to argue thatscience is ultimately a sham, that we scientists read order into nature, not out of nature, and that the laws of physicsare our laws, not nature's. I believe this is arrant nonsense. You would be hard-pressed to convince a physicist thatNewton's inverse square law of gravitation is a purely cultural concoction. The laws of physics, I submit, reallyexist in the world out there, and the job of the scientist is to uncover them, not invent them. True, at any giventime, the laws you find in the textbooks are tentative and approximate, but they mirror, albeit imperfectly, a reallyexisting order in the physical world. Of course, many scientists do not recognize that in accepting the reality of anorder in nature-the existence of laws `out there' – they are adopting a theological world view. P. C. W. Davies (1995). (shrink)

Nancy Cartwright argues that so-called capacities, not universal laws of nature, best explain the often complex way events actually unfold. On this view, science would represent a world that is fundamentally "dappled", or disunified, and not, as orthodoxy would perhaps have it, a world unified by universal laws of nature. I argue, first, that the problem Cartwright raises for laws of nature seems to arise for capacities too, so why reject laws of nature? Second, that in so far as there (...) is a problem, it concerns the role of counterfactuals in explanation; I then briefly propose a simple model of counterfactual explanation. Finally, I investigate how a sophisticated version of the regularity theory of laws of nature (that of Ramsey-Lewis) can be neutral between the empirical hypotheses that the world is unified, and that the world is disunified. (shrink)

David Lewis has proposed an analysis of lawhood in terms of membership of a system of regularities optimizing simplicity and strength in information content. This article studies his proposal against the broader background of the project of Humean supervenience. In particular, I claim that, in Lewis's account of lawhood, his intuition about small deviations from a given law in nearby worlds (in order to avoid backtracking and epiphenomena) leads to the conclusion that laws do not support (certain) counterfactuals and do (...) not bestow nomic necessity on (certain) facts induced by these laws. Support of counterfactuals and nomic necessity, however, are widely held to be important aspects of the concept of lawhood. In my view, therefore, it is not possible to abandon these criteria in any satisfactory analysis of the notion of laws of nature. In a final section, I suggest that the whole project of Humean supervenience is misleading. It does not sufficiently take notice of the important role that reasoning about contrary-to-fact situations plays in modern scientific practice. (shrink)

This is the first part of a two-part article in which we defend the thesis of Humean Supervenience about Laws of Nature (HS). According to this thesis, two possible worlds cannot differ on what is a law of nature unless they also differ on the Humean base. The Humean base is easily to characterize intuitively, but there is no consensus on how, precisely, it should be defined. Here in Part I, we present and motivate a characterization of the Humean base (...) that, we argue, enables HS to capture what is really stake in the debate, without taking on extraneous commitments. (shrink)

A law about frequencies would be a law of nature that imposes a constraint on one or more (actual, global) frequencies. On any of the leading philosophical approaches to laws of nature, there could be laws about frequencies. Hypotheses that posit laws about frequencies turn out to behave very similarly to hypotheses that posit corresponding laws about probabilities or chances -- they make the same predictions, provide similar explanations, and are confirmed or disconfirmed by empirical evidence in the same ways. (...) This makes it interesting to consider the possibility of interpreting probabilistic laws from scientific theories as laws about frequencies. This is surprising proposal, but I argue that the resulting view (which I call 'nomic frequentism') is able to overcome all of the standard objections to frequentist interpretation of objective probabilities. (shrink)

Recently, proponents of Humean Supervenience have challenged the plausibility of the intuition that the laws of nature 'govern', or guide, the evolution of events in the universe. Certain influential thought experiments authored by John Carroll, Michael Tooley, and others, rely strongly on such intuitions. These thought experiments are generally regarded as playing a central role in the lawhood debate, suggesting that the Mill-Ramsey-Lewis view of the laws of nature, and the related doctrine of the Humean Supervenience of laws, are false. (...) In this paper, I take on these recent challenges, arguing that the intuition that the laws govern should be taken seriously. Still, I find the recent discussions insightful, in certain ways. Employing some ideas from one of the critics (Barry Loewer), I draw some non-standard conclusions about the significance of the thought experiments to the lawhood debate. (shrink)

Could there be a concept of a law of nature which allows the laws to have exceptions? The prospect of the existence of such laws sounds bleak for it cannot be denied that exceptions to laws usually count straightforwardly as falsifications: it is generally held that laws, whatever else they might be, are or give rise to strict universal regularities. Yet, some proponents of so called ‘ceteris paribus laws’ believe that even the most fundamental laws of nature, like the laws (...) of physics, have exceptions. I argue, however, that those claims are based on a misinterpretation. Failures of predictions on the basis of laws have been wrongly identified with exceptions to the laws themselves. Once a proper distinction between the two cases has been made—I call them ‘pseudo’ versus ‘real’ exceptions—the arguments from ceteris paribus laws break down. However, the question whether laws can have real exceptions is still pressing and it asks for novel approaches: Philosophers have long agreed that although universality is necessary for lawhood it is not sufficient: a law statement must be a universal generalisation plus some X. I suggest, instead, that approximate universality plus some X is enough for lawhood. The hope is simply that we have overpaid the bill with the additional X such that we can demand cash back which comes in the currency of exceptions. I will discuss four such Xs: two for fundamental laws, namely David Armstrong’s nomological necessity and David Lewis’s membership in a best deductive system. Of these two Xs Lewis's will turn out to be well suited to the task: there could indeed be Lewis-laws with exceptions. I will argue, however, that necessitarians like Armstrong would have to face some metaphysical difficulties, if they wished to incorporate the possibility for exceptions into their theory. Next to fundamental laws I also discuss two types of non-fundamental laws. One type, emergent laws, which I have modelled after Lewis’s X idea, also allow for exceptions. Laws of the other type, grounded laws, inherit their law status from underlying laws and can tolerate real exceptions if and only if fundamental laws can. On the whole, the outcome of my thesis is still only modestly positive. I will reveal that how we speak of the laws depends on whether we focus on their linguistic codification or on the lawful and exceptional events. A conservative, language centered interpretation of my findings could suggest that all laws remain strict after all. (shrink)

This paper explores whether it is possible to reformulate or re-interpret Lewis’s theory of fundamental laws of nature—his “best system analysis”—in such a way that it becomes a useful theory for special science laws. One major step in this enterprise is to make plausible how law candidates within best system competitions can tolerate exceptions—this is crucial because we expect special science laws to be so called “ceteris paribus laws”. I attempt to show how this is possible and also how we (...) can thereby make the first step towards a solution for the infamous difficulties surrounding the troublesome ceteris paribus clause. The paper outlines the general ideas of the theory but also points out some of its difficulties and background assumptions. (shrink)

Dispositions are related to conditionals. Typically a fragile glass will break if struck with force. But possession of the disposition does not entail the corresponding simple (subjunctive or counterfactual) conditional. The phenomena of finks and antidotes show that an object may possess the disposition without the conditional being true. Finks and antidotes may be thought of as exceptions to the straightforward relation between disposition and conditional. The existence of these phenomena are easy to demonstrate at the macro-level. But do they (...) exist at the fundamental level also? While fundamental finkish dispositions may be excluded fairly straightforwardly, the existence of fundamental antidotes is more open. Nonetheless I conclude that the phenomenon is likely to be less widespread than at the macro level and that fundamental antidotes may be eliminable. According to the dispositional essentialist, the laws of nature can be explained by taking natural properties to be essentially dispositional. This account can be extended to show that the existence of finks and antidotes explains ceteris paribus laws. Consequently the existence or otherwise of fundamental finks and antidotes sheds some light on the question of whether fundamental laws may also be ceteris paribus laws. (shrink)

Opponents of ceteris paribus laws are apt to complain that the laws are vague and untestable. Indeed, claims to this effect are made by Earman, Roberts and Smith in this volume. I argue that these kinds of claims rely on too narrow a view about what kinds of concepts we can and do regularly use in successful sciences and on too optimistic a view about the extent of application of even our most successful non-ceteris paribus laws. When it comes to (...) testing, we test ceteris paribus laws in exactly the same way that we test laws without the ceteris paribus antecedent. But at least when the ceteris paribus antecedent is there we have an explicit acknowledgment of important procedures we must take in the design of the experiments — i.e., procedures to control for “all interferences” even those we cannot identify under the concepts of any known theory. (shrink)

In this paper the claim that laws of nature are to be understood as claims about what necessarily or reliably happens is disputed. Laws can characterize what happens in a reliable way, but they do not do this easily. We do not have laws for everything occurring in the world, but only for those situations where what happens in nature is represented by a model: models are blueprints for nomological machines, which in turn give rise to laws. An example from (...) economics shows, in particular, how we use--and how we need to use--models to get probabilistic laws. (shrink)

This paper discusses the relationship between dispositions and laws and the prospects for any analysis of talk of laws in terms of talk of dispositions. Recent attempts at such a reduction have often been motivated by the desire to give an account of ceteris paribus laws and in this they have had some success. However, such accounts differ as to whether they view dispositions as properties fundamentally of individuals or of kinds. I argue that if dispositions are properties of individuals, (...) we cannot give a complete account of ceteris paribus laws. Alternatively, if dispositions are properties of kinds, any reductive analysis of laws would require an extension of the notion of the dispositional beyond its usual meaning so that in effect there can be no reduction of laws to dispositions as traditionally understood. An attempt to reduce the nomological to the dispositional is therefore not the way to provide a unified account of traditional and ceteris paribus laws. (shrink)

Given its importance in modern physics, philosophers of science have paid surprisingly little attention to the subject of symmetries and invariances, and they have largely neglected the subtopic of symmetry breaking. I illustrate how the topic of laws and symmetries brings into fruitful interaction technical issues in physics and mathematics with both methodological issues in philosophy of science, such as the status of laws of physics, and metaphysical issues, such as the nature of objectivity.

Much of the literature on ceteris paribus laws is based on a misguided egalitarianism about the sciences. For example, it is commonly held that the special sciences are riddled with ceteris paribus laws; from this many commentators conclude that if the special sciences are not to be accorded a second class status, it must be ceteris paribus all the way down to fundamental physics. We argue that the (purported) laws of fundamental physics are not hedged by ceteris paribus clauses and (...) provisos. Furthermore, we show that not only is there no persuasive analysis of the truth conditions for ceteris paribus laws, there is not even an acceptable account of how they are to be saved from triviality or how they are to be melded with standard scientific methodology. Our way out of this unsatisfactory situation to reject the widespread notion that the achievements and the scientific status of the special sciences must be understood in terms of ceteris paribus laws. (shrink)

Many have claimed that ceteris paribus (CP) laws are a quite legitimate feature of scientific theories, some even going so far as to claim that laws of all scientific theories currently on offer are merely CP. We argue here that one of the common props of such a thesis, that there are numerous examples of CP laws in physics, is false. Moreover, besides the absence of genuine examples from physics, we suggest that otherwise unproblematic claims are rendered untestable by the (...) mere addition of the CP operator. Thus, “CP all Fs are Gs” when read as a straightforward statement of fact, cannot be the stuff of scientific theory. Rather, we suggest that when ``ceteris paribus'' appears in scientific works it plays a pragmatic role of pointing to more respectable claims. (shrink)

Nancy Cartwright (1983, 1999) argues that (1) the fundamental laws of physics are true when and only when appropriate ceteris paribus modifiers are attached and that (2) ceteris paribus modifiers describe conditions that are almost never satisfied. She concludes that when the fundamental laws of physics are true, they don't apply in the real world, but only in highly idealized counterfactual situations. In this paper, we argue that (1) and (2) together with an assumption about contraposition entail the opposite conclusion (...) — that the fundamental laws of physics do apply in the real world. Cartwright extracts from her thesis about the inapplicability of fundamental laws the conclusion that they cannot figure in covering-law explanations. We construct a different argument for a related conclusion — that forward-directed idealized dynamical laws cannot provide covering-law explanations that are causal. This argument is neutral on whether the assumption about contraposition is true. We then discuss Cartwright's simulacrum account of explanation, which seeks to describe how idealized laws can be explanatory. (shrink)

Debate over the nature of science has recently moved from the halls of academia into the public sphere, where it has taken shape as the "science wars." At issue is the question of whether scientific knowledge is objective and universal or socially mediated, whether scientific truths are independent of human values and beliefs. Ronald Giere is a philosopher of science who has been at the forefront of this debate from its inception, and Science without Laws offers a much-needed mediating perspective (...) on an increasingly volatile line of inquiry. Giere does not question the major findings of modern science: for example, that the universe is expanding or that inheritance is carried by DNA molecules with a double helical structure. But like many critics of modern science, he rejects the widespread notion of science--deriving ultimately from the Enlightenment--as a uniquely rational activity leading to the discovery of universal truths underlying all natural phenomena. In these highly readable essays, Giere argues that it is better to understand scientists as merely constructing more or less abstract models of limited aspects of the world. Such an understanding makes possible a resolution of the issues at stake in the science wars. The critics of science are seen to be correct in rejecting the Enlightenment idea of science, and its defenders are seen to be correct in insisting that science does produce genuine knowledge of the natural world. Giere is utterly persuasive in arguing that to criticize the Enlightenment ideal is not to criticize science itself, and that to defend science one need not defend the Enlightenment ideal. Science without Laws thus stakes out a middle ground in these debates by showing us how science can be better conceived in other ways. (shrink)

Taking seriously the arguments of Earman, Roberts and Smith that ceteris paribus laws have no semantics and cannot be tested, I suggest that ceteris paribus claims have a kind of formal pragmatics, and that at least some of them can be verified or refuted in the limit.

In this paper I defend fundamental physical laws from the arguments mounted by Nancy Cartwright in her (1999) book The Dappled World (and other publications). I argue, positively, that we have a good deal of evidence for mathematical laws—not just causal capacities—underlying many natural phenomena. I also argue, negatively, that Cartwright's main arguments unfairly demand that a fundamentalist be a strong reductionist.

Laws are supposed to tell us how physical systems actually behave. The analysis of an important part of physical practice--abstraction--shows, however, that laws describe the behavior of physical systems under very special circumstances, namely when they are isolated. Nevertheless, laws are applied in cases of non-isolation as well. This practice requires an explanation. It is argued that one has to assume that physical systems have dispositions. I take these to be innocuous from an empiricist's standpoint because they can--at least in (...) principle--be measured. Laws can be applied whenever such a disposition is present, they describe how the physical system would behave if the disposition were manifest. (shrink)