The Sources of Necessity: Essence, Laws, and Logic
Part I: The Framework
Part II: The Sources
Part III: The Problems
Part I: The Framework
Chapter 1: Explanatory Phenomena
I introduce “explanatory phenomena” as those phenomena that establish objective, generative explanations. I motivate the view that there are four explanatory phenomena, essences, laws of nature, laws of metaphysics, and logical consequence. Their “power to explain” is a mysterious power to reach into the world of facts and to make-it-so that facts obtain. I argue that this power to explain requires a substantive metaphysical analysis in terms of necessity. I develop such an analysis, the Modal-Axiomatic Account, and defend it against objections. The remainder of the book develops various consequences of the account.
Chapter 2: Manners of Exertion
This chapter accounts for important differences between explanatory phenomena. I begin by identifying explanatory phenomena with “sources of necessity” which exert necessity on facts. I characterize their respective “manners of exertion” in terms of different modal axioms. These modal principles characterize the ways in which a source interacts with the world of facts. We can use this to capture intuitive job description, including the “governing” work of laws, the “constraining” work of essences, or the “transferring” work of logic. I argue that each source exerts necessity in one particular manner, and I give an overview of their manners of exertion, which I defend in Part II.
Chapter 3: Nature of Necessity
This chapter argues for two claims about the nature of necessity. I will defend Moorean Modal Primitivism. The view consider necessity a primitive phenomenon. It is Moorean because it requires that all necessity-facts are grounded in facts involving sources of necessity. The view contrasts with Bob Hale’s brand of modal primitivism, and it contrasts with Kit Fine’s reductive view about metaphysical necessity. I will also defend Moderate Modal Pluralism. That view is pluralistic because it says that familiar kinds of necessity, such as metaphysical and natural necessity, are equally fundamental. It is moderate because it defines the kinds of necessity from a generic notion of necessity and the exerting source. The chapter defends the two views and develops two problems, the problem of the necessity of sources, and the problem of relative strength, which I discuss to in Part III.
Part II: The Sources
Chapter 4: Governance of Laws of Nature
This chapter uses the Modal-Axiomatic Account to develop the governing conception of laws of nature. It first develops a version of the necessitation-based account familiar from Dretske and Armstrong, and then goes on to criticize these views. I argue that necessitation-based accounts do not allow for indeterministic governance. My main opponent is Armstrong’s view that indeterministic laws operate with degrees of necessitation. I then develop my own “conferral” conception of governance, on which laws render disjunctions of future facts hypothetically necessary. The real job of natural laws, on this view, is to generate spaces of possible outcomes for the causal sequence. Causal effects are downstream from these possibilities.
Chapter 5: Essences and Modal Logicism
This chapter investigates how essences and logic exert necessity. I argue against the “dual source view”, on which essences and logic exert two distinct kinds of necessity. That view is problematic because it entails that essence-violations are genuinely possible. There are two alternative “creation and propagation views”, according to which one of essence and logic creates the strongest kind of necessity, while the other one propagates it to further truths. According to Essentialism, essence is the source of the strongest kind of necessity, and according to Modal Logicism, logic is the source of the strongest kind of necessity. The chapter spends some time on developing these two views, and on showing that they are both serious contenders. I then develop the main argument of the chapter, which I intend to show that Modal Logicism is unable to capture genuine necessity de re. The upshot is that while essence is a directly conferring source, logic is a transferring source of necessity.
Chapter 6: Laws of Metaphysics
The goal of this chapter is to argue that laws of metaphysics are a distinctive source of necessity. Metaphysical laws are not reducible to essences, nor are they of the same kind as laws of nature. I begin with a characterization of the constructional conception of metaphysical laws. I will then pursue two main lines of argument. I will argue that metaphysical laws have a distinctive manner of exertion, which is different from that of essences and from that of natural laws. I will, secondly, argue that laws of metaphysics exert a distinctive kind of necessity, which is weaker than the necessity exerted by essence and stronger than the necessity exerted by natural laws.
Part III: The Problems
Chapter 7: Necessity of Sources
This chapter argues that essence-facts (“it is essential that p”), law-facts (“it is a law that p”), and logic-facts (“it is a logical truth that p”) are necessary, and it develops explanations for these necessity-facts. I use a version of Blackburn’s famous dilemma to argue for the necessity of source-facts, and to argue against a range of familiar solutions. I then develop a solution in terms of Kit Fine’s notion of “unworldly truths”. Since I don’t take that notion to be in good standing, I analyze it in terms of an “anchored conception” of possibility, on which genuine notions of possibility are defined relative to all facts that are metaphysically prior to the possibilities. Essence-facts and logic-facts are necessary because they are unworldly-truths, which means that they feature in the anchor of possibility. I augment this solution with certain additional assumptions to explain the necessity of law-facts.
Chapter 8: Relative Modal Strength
This chapter begins with an ordering of strength over different kinds of necessity. Essences exert the strongest kind, metaphysical laws the second strongest, and natural laws the weakest. I then contrast the familiar entailment-conception of modal strength with an intrinsic conception, on which modal strength is akin to degrees of necessity. I argue for the entailment-conception, and then explain why modal pluralists appear to be unable to capture differences in modal strength thus understood. But appearances are misleading. I recover the entailment from a stronger to a weaker kind of necessity with the help of two assumptions. The first of these assumptions is the anchored conception of possibility from Chapter 7. The second assumption is the “Priority of Possibility”, according to which a contingent fact’s possibility is metaphysically prior to that fact.
Chapter 9: Metaphysical Cosmogony
This final chapter aims to provide a foundation for the anchored conception of possibility from Chapter 7 and the Priority of Possibility from Chapter 8. I develop the view on which reality is one big unfolding sequence that starts from essences and logic, which generate absolute possibilities, which in turn give rise to metaphysical laws, which generate metaphysical possibilities, and so on. The crucial idea (familiar from Chapter 4) is that conferring sources generate spaces of possibility, which give rise to further facts in an indeterministic fashion. Using this indeterministic mechanism, I will develop a cosmogenic sequence that runs from logic and essences all the way to the contingent facts. I contrast my view with familiar deterministic versions of metaphysical rationalism, and I argue that an indeterministic cosmogenic sequence offers serious explanatory benefits. I end by defining the sources of necessity in terms of their position in the cosmogenic sequence.