Online research in philosophy

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.

Some scientists try to discover and report laws of nature. And, they do so with success. There are many principles that were for a long time thought to be laws that turned out to be useful approximations, like Newton’s gravitational principle. There are others that were thought to be laws and still are considered laws, like Einstein’s principle that no signals travel faster than light. Laws of nature are not just important to scientists. They are also of great interest to us philosophers, though primarily in an ancillary way. Qua philosophers, we do not try to discover what the laws are. We care about what it is to be a law, about lawhood, the essential difference between something’s being a law and something’s not being a law. It is one of our jobs to understand lawhood and convey our understanding to others.

Scientific essentialism aims to account for the natural laws' special capacity to support counterfactuals. I argue that scientific essentialism can do so only by resorting to devices that are just as ad hoc as those that essentialists accuse Humean regularity theories of employing. I conclude by offering an account of the laws' distinctive relation to counterfactuals that portrays laws as contingent but nevertheless distinct from accidents by virtue of possessing a genuine variety of necessity.

Marc Lange objects to scientific essentialists that they can give no better account of the counterfactual invariance of laws than Humeans. While conceding this point succeeds ad hominem against some essentialists, I show that it does not undermine essentialism in general. Moreover, Lange's alternative account of the relation between laws and counterfactuals is - with minor modification - compatible with essentialism.

Suppose that unobtanium-346 is a rare radioactive isotope. Consider: (1) Every Un346 atom, at its creation, decays within 7 microseconds (µs). (50%) Every Un346 atom, at its creation, has a 50% chance of decaying within 7µs. (1) and (50%) can be true together, but (1) and (50%) cannot together be laws of nature. Indeed, (50%)'s mere (non-vacuous) truth logically precludes (1)'s lawhood. A satisfactory analysis of chance and lawhood should nicely account for this relation. I shall argue first that David Lewis's Humean picture accounts for this relation only by inserting this relation ‘by hand’. Next, I shall argue that this relation between law and chance also threatens a radically non-Humean picture of laws and chances. Finally, I shall offer an account of natural law that nicely explains the relation between chancy facts and deterministic laws. This explanation is not ad hoc because it derives the relation from the very same features of lawhood that account for the laws' special relation to counterfactuals and explain how the laws (unlike the accidents) possess a variety of necessity. The reason that a chancy fact such as (50%) keeps (1) from being a law, without keeping (1) from being true, is ultimately that a chancy fact constrains the subjunctive facts and (1)'s lawhood, unlike (1)'s truth, depends upon the subjunctive facts.

The paper defends Humean approaches to autonomous mental causation against recent attacks in the literature. One important criticism launched at Humean approaches says that the truth-makers of the counterfactuals in question include laws of nature, and there are laws that support physical-to-physical counterfactuals, but no laws in the same sense that support mental-to-physical counterfactuals. This paper argues that special science causal laws and physical causal laws cannot be distinguished in terms of degrees of strictness. It follows that mental-to-physical counterfactuals are supported—or not supported—by laws in just the same way as are physical-to-physical counterfactuals.

This paper develops an account of explanation in biology which does not involve appeal to laws of nature, at least as traditionally conceived. Explanatory generalizations in biology must satisfy a requirement that I call invariance, but need not satisfy most of the other standard criteria for lawfulness. Once this point is recognized, there is little motivation for regarding such generalizations as laws of nature. Some of the differences between invariance and the related notions of stability and resiliency, due respectively to Sandra Mitchell and Brian Skyrms, are explored.

Ceteris-paribus clauses are nothing to worry about; aceteris-paribus qualifier is not poisonously indeterminate in meaning. Ceteris-paribus laws teach us that a law need not be associated straightforwardly with a regularity in the manner demanded by regularity analyses of law and analyses of laws as relations among universals. This lesson enables us to understand the sense in which the laws of nature would have been no different under various counterfactual suppositions — a feature even of those laws that involve no ceteris-paribus qualification and are actually associated with exceptionless regularities. Ceteris-paribus generalizations of an‘inexact science’ qualify as laws of that science in virtue of their distinctive relation to counterfactuals: they form a set that is stable for the purposes of that field. (Though an accident may possess tremendous resilience under counterfactual suppositions, the laws are sharply distinguished from the accidents in that the laws are collectively as resilient as they could logically possibly be.) The stability of an inexact science's laws may involve their remaining reliable even under certain counterfactual suppositions violating fundamental laws of physics. The ceteris-paribus laws of an inexact science may thus possess a kind of necessity lacking in the fundamental laws of physics. A nomological explanation supplied by an inexact science would then be irreducible to an explanation of the same phenomenon at the level of fundamental physics. Island biogeography is used to illustrate how a special science could be autonomous in this manner.

Why should science be so interested in discovering whether p is a law over and above whether p is true? The answer may involve the laws' relation to counterfactuals: p is a law iff p would still have obtained under any counterfactual supposition that is consistent with the laws. But unless we already understand why science is especially concerned with the laws, we cannot explain why science is especially interested in what would have happened under those counterfactual suppositions consistent with the laws. It is argued that the laws form the only non-trivially "stable" set, where "stability" is invariance under a certain range of counterfactual suppositions not itself defined by reference to the laws. It is then explained why science should be so interested in identifying a non-trivially "stable" set: because of stability's relation to the best set of "inductive strategies".

Many philosophers have believed that the laws of nature differ from the accidental truths in their invariance under counterfactual perturbations. Roughly speaking, the laws would still have held had q been the case, for any q that is consistent with the laws. (Trivially, no accident would still have held under every such counterfactual supposition.) The main problem with this slogan (even if it is true) is that it uses the laws themselves to delimit qs range. I present a means of distinguishing the laws (and their logical consequences) from the accidents, in terms of their range of invariance under counterfactual antecedents, that does not appeal to physical modalities (or any cognate notion) in delimiting the relevant range of counterfactual perturbations. I then argue that this approach explicates the sense in which the laws possess a kind of necessity.