John T. Roberts

CETERIS PARIBUS, THERE IS NO PROBLEM OF PROVISOS

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.

A Puzzle about Laws, Symmetries and Measurability

I describe a problem about the relations among symmetries, laws and measurable quantities. I explain why several ways of trying to solve it will not work, and I sketch a solution that might work. I discuss this problem in the context of Newtonian theories, but it also arises for many other physical theories. The problem is that there are two ways of defining the space-time symmetries of a physical theory: as its dynamical symmetries or as its empirical symmetries. The two definitions are not equivalent, yet they pick out the same extension. This coincidence cries out for explanation, and it is not clear what the explanation could be. 1. The Puzzle: Symmetries, Measurability and Invariance 1.1 The symmetries and the measurable quantities of Newtonian mechanics 1.2 The puzzle2. Two Easy Answers3. Another Unsuccessful Solution: Appeal to Geometrical Symmetries4. Locating the Puzzle5. The Relation between Laws and Measurability6. A Possible Solution The Puzzle: Symmetries, Measurability and Invariance 1.1 The symmetries and the measurable quantities of Newtonian mechanics 1.2 The puzzle Two Easy Answers Another Unsuccessful Solution: Appeal to Geometrical Symmetries Locating the Puzzle The Relation between Laws and Measurability A Possible Solution

Leibniz on Force and Absolute Motion

I elaborate and defend an interpretation of Leibniz on which he is committed to a stronger space‐time structure than so‐called Leibnizian space‐time, with absolute speeds grounded in his concept of force rather than in substantival space and time. I argue that this interpretation is well‐motivated by Leibniz’s mature writings, that it renders his views on space, time, motion, and force consistent with his metaphysics, and that it makes better sense of his replies to Clarke than does the standard interpretation. Further, it illuminates the way in which Leibniz took his physics to be grounded in his metaphysics.

Some Laws of Nature are Metaphysically Contingent

Laws of nature are puzzling because they have a ‘modal character’—they seem to be ‘necessary-ish’—even though they also seem to be metaphysically contingent. And it is hard to understand how contingent truths could have such a modal character. Scientific essentialism is a doctrine that seems to dissolve this puzzle, by showing that laws of nature are actually metaphysically necessary. I argue that even if the metaphysics of natural kinds and properties offered by scientific essentialism is correct, there are still some metaphysically contingent truths that share the modal character of the laws of nature. I argue that these contingent truths should be considered laws of nature. So even if scientific essentialism is true, at least some laws of nature are metaphysically contingent.

Measurability And Physical Laws

I propose and motivate a new account of fundamental physical laws, the Measurability Account of Laws (MAL). This account has a distinctive logical form, in that it takes the primary nomological concept to be that of a law relative to a given theory, and defines a law simpliciter as a law relative to some true theory. What makes a proposition a law relative to a theory is that it plays an indispensable role in demonstrating that some quantity posited by that theory is measurable. In Section 1, I motivate the project of seeking a philosophical account of fundamental physical laws, as opposed to laws of nature in general. In Section 2, I motivate seeking an account with the distinctive logical form of the MAL. In Section 3, I present the MAL and illustrate the way it works by applying it to a simple example.

Chance without Credence

It is a standard view that the concept of chance is inextricably related to the technical concept of credence. One influential version of this view is that the chance role is specified by (something in the neighborhood of) David Lewiss Principal Principle, which asserts a certain definite relation between chance and credence. If this view is right, then one cannot coherently affirm that there are chance processes in the physical world while rejecting the theoretical framework in which credence is defined, namely the Bayesian framework. This is surprising; why should adopting a theory that says there are chances at work in nature put any particular constraints on our theorizing about epistemology and rational choice? It is quite plausible that in order for anything to count as the referent of our concept chance, it would have to be related to epistemic rationality in a certain way—roughly, it is rational to have more confidence that something will happen the greater you think its chance is. But this commonsensical idea does not seem to be inherently committed to any particular theoretical approach to rationality, so why should we think that adopting the Bayesian approach is a prerequisite for thinking coherently about chance? I propose and defend a replacement for the Principal Principle which makes no use of the concept of credence. I also argue that this replacement is advantageous for the project of theorizing about the nature of chance. 1 The Entanglement of Chance with Credence 2 Desiderata for a Replacement for PP 3 Disentangling Chance from Credence 4 What RP Demands of a Bayesian Subject 5 How Narrowly RP Constrains the Chance Function 6 An Objection 7 An Unexpected Benefit 8 Conclusion Appendix A: Any Subject with Credences who Obeys PP also Obeys RP Appendix B: Any Subject with Credences who Obeys RP also Approximately Obeys PP 1 The Entanglement of Chance with Credence 2 Desiderata for a Replacement for PP 3 Disentangling Chance from Credence 4 What RP Demands of a Bayesian Subject 5 How Narrowly RP Constrains the Chance Function 6 An Objection 7 An Unexpected Benefit 8 Conclusion Appendix A: Any Subject with Credences who Obeys PP also Obeys RP Appendix B: Any Subject with Credences who Obeys RP also Approximately Obeys PP