Quantum Action and Substance Causation

This article is an introduction to the Synthese Special Issue, Natural Kinds: Language, Science, and Metaphysics. The issue includes new contributions to some of the main questions involved in the present philosophical debates on natural kinds and on natural kind terms. Those debates are relevant to philosophy of language, philosophy of science, and metaphysics. In philosophy of language it is highly debated what the meaning of natural kind terms is, how their reference is determined, as well as whether there are differences and similarities between the semantics of natural kind terms and that of other sorts of kind terms. In philosophy of science, natural kinds are relevant because they are the basis for scientific classifications and play an explanatory role in scientific theories; thus one aim of science is to discover natural kinds and theorize about them. Natural kinds are also relevant in metaphysics, where many questions involving natural kinds are debated and especially those concerning the sort of entities we refer to when using natural kind terms, i.e., the ontological status of natural kinds; in this regard there are different views, such as conventionalism, realism and essentialism. Another metaphysical question is what it is that characterizes the naturalness of kind divisions. The introduction sketches the antecedents of some of the present views on natural kinds and natural kind terms, and indicates some of the topics dealt with in the articles that make up the issue, which can be classified in the following groups: (1) the metaphysics and epistemology of natural kinds (2) the semantics of natural kind terms and other kind terms (3) questions on species and (4) other related issues on natural kinds. However, many of the articles cover more than just one of these topics.

Preface. Introduction: Natural Kinds and Other Assorted Concepts P.J. Riggs. On the Necessity of Natural Kinds J. Collier. Natural Kinds and Natural Kind Reasoning B. Ellis. The Jerrybuilt House of Humeanism C. Lierse. Physical Necessity and the Passage of Time P. Forrest. Theorizing and Empirical Belief F.J. Clendinnen. Indifference and Induction L. O'Neill. Towards Metamethodology: For the History and Philosophy of Science J. Fox. Elk Theories: A Galilean Strategy for Validating a New Scientific Discovery N. Thomason. Of Crows and Quarks: Reflections on the Laws of Quantum Mechanics A. Heathcote. Laws and States in Quantum Mechanics J. Forge. Instrumental Theories: Possibilities and Space and Time I. Hinckfuss. Spacetime or Quantum Particles: The Ontology of Quantum Gravity? P.J. Riggs. Comments on Lierse D.M. Armstrong. Comments on Forge A. Heathcote. Comments on Thomason K. Hutchison. Index.

I outline a hylomorphic account of physical reality in which the cosmos as a whole has mental properties which explain its nomological order. According to this theory, the cosmos is directed in its temporal development toward certain ends or goals which it intends, and these ends are immanent to the cosmos rather than being imposed upon it. My object in doing so is to argue that, contrary to Sean Carroll (2021), a view of physical reality as having intrinsically mental aspects need not induce any modifications of the known laws of physics nor violate 'causal closure' under physical laws. Rather, this soft form of naturalism, which includes final causes within nature, provides a foundation for the laws of physics that is lacking in Carroll's hard form of naturalism, which excludes mind from fundamental reality. I propose a trilemma for Carroll in which he should either: abandon naturalism, by admitting that the laws of physics are imposed by a divine mind; abandon realism, by conceding that 'laws' are constructed by human minds; or embrace cosmopsychism, by acknowledging that the cosmos as a whole instantiates a mind. I argue that cosmic hylomorphism, which links consciousness with intentional cognition, is preferable to non-hylomorphic versions of cosmopsychism, which tend to prioritize consciousness over intentionality.

DIVINE ACTION, DETERMINISM, AND THE LAWS OF NATURE by Jeffrey Koperski. New York: Routledge, 2020. 168 pages. Hardcover; $160.00. ISBN: 9780367139001. Ebook; open access. *When it comes to talking about God's action in the world and laws of nature in the science classes I teach, my students sometimes wonder if God, violating the very laws he created, is a problem. Jeffrey Koperski has written a book for those students and for you, too! You can see that Koperski is a teacher well experienced with explaining philosophical ideas to students majoring in anything but philosophy (who form the bulk of our philosophy teaching). This makes his new book a very accessible and enjoyable read. Moreover, no matter your background, you are likely to learn something new reading this book, perhaps even about your favored approach to divine action in the world. *Koperski is right to point out that philosophy of science--particularly philosophy of physics--is missing from most divine action discussions. If it enters at all, philosophy of science makes only cursory contributions. He is also right to observe that the causal closure of the physical, or of nature as a whole, gets too little attention in the divine action literature despite the outsized role it plays. Koperski ably shows why neither causal closure nor determinism are genuine obstacles to divine action in the world. Philosophy of science allows Koperski to clear a lot of this dead brush from the ground of divine action literature. This is an important contribution to the discussions. *Koperski helps us think more accurately about laws of nature (full disclosure: he and I have talked about these issues and tread a lot of the same ground). The assumption or metaphor of laws as "governing" events in nature has been accepted as largely unanalyzed in the divine action literature. Though he rarely uses this language, Koperski shows why the metaphor of laws "governing" things does not stand up to close analysis. He endorses a view of laws functioning as constraints that enables us to think more clearly about how God can act in the world without violating laws. *Koperski describes his model for divine action as decretalist and nonviolationist. The laws that scientists deal with represent divine decrees--gifts of order and constraint to creation. The regularities of creation genuinely exist and genuinely act. Koperski captures a biblical view of God's relationship to creation; he also considers natural philosophers' critical thinking about laws in the seventeenth century. *As for nonviolationism, Koperski points out that laws--the nomic conditions or features of the world--do not make things go (no "governing" metaphor). Rather, as physicists have recognized, it is forces that make things move. What laws do is provide nomic constraints on the behavior of forces (p. 134). His model is nonviolationist in that these laws are not violated when God acts in nature; rather, when there are nonnomic changes, "the laws adapt to change. This was true when we thought that nature was Newtonian, and it remains true in the age of quantum mechanics and relativity" (p. 135). Koperski's account is consistent with what I think physics reveals to us about the laws of nature--they function as typicality conditions: A law tells us what to expect for the behavior of forces on a system typical for the constraints represented by the law. But when new factors or conditions are introduced, the law does not tell us what to expect. The typicality is shattered, but not the law. Yet, this does not distress physicists; we know how to model and calculate what happens with these additional factors that the original law did not cover. *Consider a simple example: A grandfather clock keeps time well because of the lawlike regularities involved in its functioning. Yet, if I use my finger to keep the minute hand from moving forward, the clock will cease keeping time accurately. No laws have been violated; however, a genuine physical change has taken place regarding the clock's functioning. The regularities are still there--the laws are still operative--but they adapt to the presence of a new effect or force introduced into the clock system. What this means is that "once the laws of nature are distinguished from the behavior that is the result of those laws and nonnomic conditions, we find a vast space of contingency in which God can act" (p. 135). Koperski calls this a "neoclassical model of special divine action" (p. 135) because God is not manipulating laws to act in the world. If humans can make genuine nonnomic changes to nature without violating laws (e.g., rockets that overcome gravity's pull), clearly God is able to. The question then becomes one of God's relationship to the contingent order he has given creation. *You may be thinking of possible objections to this account of divine action. Koperski discusses several and I recommend you read what he has to say about them. I will briefly discuss what seem to be the most serious--that is, possible violations of energy conservation. There are many reasons to think that conservation laws function as constraints on systems when particular conditions hold. For instance, as Koperski points out, according to general relativity, energy conservation does not apply to an expanding universe. In a dynamic spacetime, the motion of objects does not conserve energy. More generally, any system whose dynamics depend on time will fail to conserve energy, and there are lots of such systems in the actual world. Physicists have precise ways of quantifying how much a system violates energy conservation and describing the resulting order of the system in question. The idea that any system violating energy conservation can always be embedded into a larger system restoring conservation is just that--an idea and nothing more. Physicists do not have any good reasons supporting this idea (though some defend it to maintain their reductionist intuitions). There is plenty of opportunity for divine action in the world and energy conservation is never an issue. *One could sweat some details. For example, Koperski rehearses arguments to the effect that quantum processes suppress chaos, thus undercutting the amplification of small quantum changes to macroworld effects (pp. 52-53). While it is true that quantum mechanics is no friend of chaos, the amplification argument is more along the lines of a chaotic macroscopic system being sensitive to quantum fluctuations; this doesn't depend on the existence of so-called quantum chaos. There always are stringent constraints on such amplification, however; so, Koperski is correct that banking on this as a route for divine action is still a hopeless cause. And I am not convinced that physics and philosophy of science are pointing toward an eventual rejection of ontological randomness in quantum mechanics (pp. 60-63). Irreducible randomness is not lawless chaos; it is a form of order that God has given to creation even if it offends the deterministic intuitions of some physicists and philosophers. None of Koperski's account stands or falls with these quibbles. *I would like to see Koperski's account enriched with the doctrine of creation, such as in Understanding Scientific Theories of Origins: Cosmology, Geology and Biology in Christian Perspective, Robert C. Bishop et al. (IVP Academic, 2018). His discussion in sec. 4.2 suggests that seventeenth-century natural philosophers eventually ditched all forms of divine-mediated action for direct or unmediated divine action as embodied in the laws of nature (the discussion is a little oversimplified, but this is a short book). This amounts to treating the laws of nature as the main mediators of all that happens in creation (back to the "governing" metaphor). In contrast, the doctrine of creation's emphasis on multiple forms of divine-mediated action helps to address the divine relationship to creation in which God is working in and through nature, not outside and apart from it. This is exactly what Koperski's account needs for some of the questions he entertains at the end of the book and for some he leaves unanswered (e.g., why one does not have to restrict divine concurrence to Thomist models only). *Reviewed by Robert C. Bishop, Department of Physics and Engineering, Wheaton College, Wheaton, IL 60187.

I first argue that Aristotelian intellectual intuition (recognizing archai through epagoge and seeing their truth by recognizing their explanatory power through nous) generates basic beliefs which are not inferred — inductively or deductively — from other beliefs. Both involve synthetic intuitive insight. Epagoge grasps a connection and nous sees its general applicability. I next argue that such beliefs are properly basic by adapting an argument made by Hilary Kornblith. According to Kornblith, the world is objectively divided into natural kinds. We humans perceive the world divided into natural kinds. There is empirical evidence suggesting that we divide the world not only as it is objectively divided, but in making inductive inferences, that is, in inferring that an object will have certain properties on the basis of its having others. This grounds the reliability of (certain) inductive inferences. But the leading principles (in Peirce’s sense) of these inferences are basic beliefs generated through intellectual intuition. Hence intellectual intuition generates certain properly basic beliefs.

This article is about the relation between classical mechanics and quantum mechanics. The question is asked: Can quantum mechanics be formulated in such a way that it looks like some sort of classical mechanics? Why do we ask such question in the first place? The answer is interesting from the point of view of interpretation of quantum mechanics. L. de Broglie [1] has pointed out that quantum mechanics has two faces: The particle interpretation and the wave interpretation. Maybe there is a third interpretation, where quantum mechanics has the face of classical mechanics. The answer is interesting also for the purpose of a proper definition, quantitative analysis and understanding of phenomena occuring in quantum physics, the definition of which comes from classical physics. Examples are quantum chaos and quantum instantons. The affirmative answer to the above question has been proposed recently in Refs.[2, 3], stating that quantum transition amplitudes can be expressed in terms of some action, called the quantum action, which has the form of the classical action but has modified parameters.

The possibility of extending the canonical formulation of quantum mechanics (QM) to a space–time symmetric form has recently attracted wide interest. In this context, a recent proposal has shown that a spacetime symmetric many-body extension of the Page and Wootters mechanism naturally leads to the so-called Quantum Action (QA) operator, a quantum version of the action of classical mechanics. In this work, we focus on connecting the QA with the well-established Feynman’s Path Integral (PI). In particular, we present a novel formalism which allows one to identify the “sum over histories” with a quantum trace, where the role of the classical action is replaced by the corresponding QA. The trace is defined in the extended Hilbert space resulting from assigning a conventional Hilbert space to each time slice and then taking their tensor product. The formalism opens the way to the application of quantum computation protocols to the evaluation of PIs and general correlation functions, and reveals that different representations of the PI arise from distinct choices of basis in the evaluation of the same trace expression. The Hilbert space embedding of the PIs also discloses a new approach to their continuum time limit. Finally, we discuss how the ensuing canonical-like version of QM inherits many properties from the PI formulation, thus allowing an explicitly covariant treatment of spacetime symmetries.

In recent years there has been a resurgence of interest in Bohmian mechanics as a numerical tool because of its local dynamics, which suggest the possibility of significant computational advantages for the simulation of large quantum systems. However, closer inspection of the Bohmian formulation reveals that the nonlocality of quantum mechanics has not disappeared-it has simply been swept under the rug into the quantum force. In this paper we present a new formulation of Bohmian mechanics in which the quantum action, S, is taken to be complex. This leads to a single equation for complex S, and ultimately complex x and p but there is a reward for this complexification-a significantly higher degree of localization. The quantum force in the new approach vanishes for Gaussian wave packet dynamics, and its effect on barrier tunneling processes is orders of magnitude lower than that of the classical force. In fact, the current method is shown to be a rigorous extension of generalized Gaussian wave packet dynamics to give exact quantum mechanics. We demonstrate tunneling probabilities that are in virtually perfect agreement with the exact quantum mechanics down to 10(-7) calculated from strictly localized quantum trajectories that do not communicate with their neighbors. The new formulation may have significant implications for fundamental quantum mechanics, ranging from the interpretation of non-locality to measures of quantum complexity.

The article focuses on the unifying and explanatory power of the selective realism defended by Anjan Chakravartty. Our main aim is twofold. First, we critically analyse the purported synthesis between entity realism and structural realism offered by the author. We give reasons to think that this unification is an inconvenient marriage. In the second step, we deal with certain controversial aspects of the intended unification among three metaphysical concepts: causation, laws of nature and natural kinds. After pointing out that Chakravartty’s conception of laws is a plausible view that a scientific realist might endorse, we contend, on the contrary, that the concept of natural kind is dispensable in the framework of Chakravartty’s realism.

Large-scale book-length treatises on natural kinds are rather few compared to the amount of discussion on the subject and not since Brian Ellis’ Scientific Essentialism perhaps has anyone attempted to build a philosophical ‘‘world view’’ around a theory of natural kinds. Most discussion about natural kinds of the last decade has restricted itself to specific issues, such as the species debate or chemical kinds, or, as in the case of LaPorte (2009), the semantic practices surrounding kind concepts and conceptual change. In this respect, Magnus’ Scientific Enquiry and Natural Kinds: From Planets to Mallards has a worthy ambition, not least for displaying how rich and informative natural kind discussion can be despite its recent characterization as a philosophical dead end (see Hacking 2007). This holds even more so because Magnus attempts this within the context of a highly naturalistic account of natural kinds, rather than a metaphysically driven approach already predisposed to metaphysical discussion (see Ellis). In this respect, while it shares much with Boyd’s (1999) approach to natural kinds, Magnus takes the opportunity to explore in more detail a broader range of implications that flow from a naturalistic approach. Scientific Enquiry does cover a wide range of philosophical issues and an even wider range of cases. The former includes realism, pluralism, pragmatism, underdetermination, and the long-standing debate about the ontological status of species (kinds or individuals?). For the latter, Magnus ranges from planets to distributed cognition to stellar constellations to kind concepts in cooking and baking. These are enrolled to test the breadth and depth of a fairly ‘‘modest’’ definition of natural kinds, which aims to distinguish natural from non-natural kinds in a scientifically reasonable way and instantiate an intuitive pragmatic form of realism.

Causal Closure and Strong Emergence in Quantum Mechanics

Untying the Gordian Knot: Process, Reality, and Context

Though biologists identify individuals as ‘male’ or ‘female’ across a broad range of animal species, the particular traits exhibited by males and females can vary tremendously. This diversity has led some to conclude that cross-animal sexes (males, or females, of whatever animal species) have “little or no explanatory power” (Dupré 1986: 447) and, thus, are not natural kinds in any traditional sense. This chapter will explore considerations for and against this conclusion, ultimately arguing that the animal sexes, properly understood, are “historical explanatory kinds”: groupings that can be scientifically significant even while their members differ radically in their current properties and particular histories. Whether this makes them full-fledged natural kinds is a question I take up at the very end.

This chapter investigates non-causal scientific explanations that work by describing how the explanandum involves stronger-than-physical necessity by virtue of certain facts (“constraints”) that possess some variety of necessity stronger than ordinary causal laws possess. In particular, the chapter offers an account of the order of explanatory priority in explanations by constraint. It examines several important examples of explanations by constraint, distinguishing their natural kinds. It gives an account of the sense in which constraints are modally stronger than ordinary causal laws and an account of why certain deductions of constraints exclusively from other constraints possess explanatory power whereas others lack explanatory power.

The stable property cluster view of natural kinds leaves the metaphysical structure of natural kinds open. The positive corollary of this feature is freedom from explaining the nature of problematic entities and that it affords natural kind status and flexibility. However, some worries are raised against this feature; the metaphysical structure of natural kinds is required for explaining their epistemic values such as inductive and explanatory power. Here I take the criticisms at face value and offer a possible metaphysical model of the SPC account that does not meddle with the merits but mitigates the worries.