Humeanismo y leyes de la naturaleza: alcance y límites

Nomological Humeanism has developed into a research program encompassing several variations on a single theme, namely, the view that laws are statements about regularities that we find in nature. After briefly revisiting an early form of nomological Humeanism in Hume’s critique of the idea of necessary connection, this article critically examines Lewis’ two-fold approach based on Humean supervenience and the best system account. We shall point out three limits of nomological Humeanism, which are widely recognized in the literature: its inadequacy in view of physical theories, its explanatory circularity, and its purported anthropomorphism, all of which advocates of nomological Humeanism have attempted to overcome Humeanism (Jaag y Loew 2020, Loewer 2004 y Massimi 2018). Lastly, we will argue that nomological Humeanism fails to provide a suitable notion of modality for laws of nature. This latter issue continues to represent a live challenge for empiricism in the philosophy of physical laws.

Humean supervenience and tripartite entanglement relations

It has been argued that Humean Supervenience (HS) is threatened by the existence of quantum entanglement relations. The most conservative strategy for defending HS is to add the problematic entanglement relations to the supervenience basis, alongside spatiotemporal relations. In this paper, I’m going to argue against this strategy by showing how certain particular cases of tripartite entanglement states – i.e. GHZ states – posit some crucial problems for this amended version of HS. Moreover, I will show that the principle of free recombination – which is strictly linked to HS – is severely undermined if we add entanglement relations to the supervenience basis. I conclude that the conservative move is very unappealing, and therefore the defender of HS should pursue other, more controversial, strategies (e.g. committing to the nomological interpretation of the wave function).

Explanatory dispositionalism

Inspired both by our ordinary understanding of the world and by reflection on science, anti-Humeanism is a growing trend in metaphysics. Anti-Humeans reject the Lewisian doctrine of Humean supervenience that the world is “just one little thing and then another”, and argue instead that dispositions, powers, or capacities provide connection and (some say) activity in nature. But how exactly are we to understand the shared commitment of this anti-Humean movement? I argue that this kind of anti-Humeanism, at its most general level, is to be understood neither as a view about ontology (the existence of certain properties) nor about fundamentality, but rather as a specific claim about what explains what.

Humean Supervenience and Possible Worlds

The position defended is compatible with a coherent development of a reductive account of modality. It is less significant for the principle of recombination than previously thought and the principle of recombination is unlikely to play successfully its role as a principle of plenitude in any event. The distinct existences principle is defended against an argument that it is necessarily false. In fact, by comparison, we have more reason to believe in the possibility of worlds in which Humean supervenience is true and there is causation, than in physicalism about phenomenal consciousness. The counterfactual theory of causation, and surrounding framework, explains why this is the appropriate verdict at which to arrive. Some aspects of the variety of causation may be understood as a determinate-determinable relation but the different vertically fundamental bases are better understood as partial realizations. Causation is one horizontally fundamental metaphysical category but there may be others.

A Variety of Causes

Metaphysicians often focus on what is vertically fundamental, appealing to grounding or truth-making, rather than what is horizontally fundamental: what must be common to any metaphysical picture of the universe. There is a case for causation being one such feature. But how should it be characterized? A revised semantics for counterfactuals provides the basis for a new counterfactual analysis of causation that is compatible with Humean supervenience but also appropriate for a non-Humean metaphysical framework. Causes (independently of their competitors) both make the chance of an effect very much greater than its mean background chance in the circumstances and actually influences the probability of the effect in this way at the time at which the effect occurred via a complete causal chain. Causation understood in this way is a non-transitive relation. It is neutral over the metaphysics of causes and effects but allows a natural way for events to be understood as one fundamental type of causation, the other being property causation. Although negative causal statements are true, there are no cases of negative causation. The analysis explains how causation involving substantial processes is only one variety of causation, others include double prevention. It allows for a variety of micro- and macro-properties to be the basis of the difference between cause and effect. Laws are patterns of causation realized in different ways in different metaphysical pictures. The analysis of causation characterizes a horizontally fundamental property whose modal character depends upon its different realizations.

Non-Causal Counterfactual Dependence and Intrinsicality

When counterfactuals hold concerning entities with properties that stand in some kind of loose existential dependency relation, counterfactual dependence only indicates a causal relationship if part of their corresponding minimal supervenience bases satisfies the analysis of causation. The idea has application even if properties are understood in ways proponents of a powers ontology recommend. An analysis of intrinsic properties in this chapter appeals to three features—External Independence, Duplication Characterization, and Maximizing Recombination—each of which, by itself, doesn’t quite work to demarcate what we have in mind. This provides a second way of approaching the issue as well as assisting with later analysis of varieties of Humean supervenience.

Humean Supervenience and the Possibility of Necessitation

We have experiences of causation and, in specific circumstances, may well have experiences of necessary connection, although our experience mischaracterizes it. An analysis of our cognitive grasp of necessary connection explains how counterfactuals successfully capture the intimate connection we take to be present between cause and effect that, when there is no necessitation, may be lacking. The notion of necessary connection between distinct existences is coherent and, according to the most plausible ways of understanding (wholly) distinct existence, cannot be ruled out. Different metaphysical categories involve different notions of distinct existence, characterized spatially or in terms of distinct arrangements. The notion should not be characterized modally.

Why Defend Humean Supervenience?

Humean Supervenience (HS) is a metaphysical model of the world according to which all truths hold in virtue of nothing but the total spatiotemporal distribution of perfectly natural, intrinsic properties. David Lewis and others have worked out many aspects of HS in great detail. A larger motivational question, however, remains unanswered: As Lewis admits, there is strong evidence from fundamental physics that HS is false. What then is the purpose of defending HS? In this paper, we argue that the philosophical merit of HS is largely independent of whether it correctly represents the world’s fundamental structure. In particular, we show that insofar as HS is an apt model of the world’s higher-level structure, it thereby provides a powerful argument for reductive physicalism and explains otherwise opaque inferential relations. Recent criticism of HS on the grounds that it misrepresents fundamental physical reality is, therefore, beside the point.

Structural problems for reductionism

Universal reductionism—the sort of project pursued by Carnap in the Aufbau, Lewis in his campaign on behalf of Humean supervenience, Jackson in From Metaphysics to Ethics, and Chalmers in Constructing the World—aims to reduce everything to some specified base, more or less austere as it may be. In this paper, I identify two constraints that a promising strategy to argue for universal reductionism needs to satisfy: the exhaustion constraint and the chaining constraint. As a case study, I then consider Chalmers’ Constructing the World, in which a priori implication, or “scrutability”, plays the role of reduction. Chalmers first divides up the total vocabulary of our language into different families, and then argues, for each family separately, that truths involving expressions in that family are scrutable from the putative base. He does not systematically address the question whether “cross-family sentences”—sentences involving expressions from more than one family—are scrutable. I shall argue that this lacuna cannot be filled, since scrutability does not allow for the exhaustion constraint and the chaining constraint to be jointly satisfied. I further suggest that Carnap’s account, in which definability plays the role of reduction, has better prospects of meeting these constraints.