Markus Schrenk, “Metaphysics of science. A Systematic and Historical Introduction”, ed. Routledge Press, 2016
Quine used to say the boundaries between various natural sciences and metaphysics are more likely useful labels for librarians. Contemporary working philosophers and scientists are sharing, according to him, a sprawling system of knowledge (Quine 1966, p.56). The questions concerning these slippery boundaries are puzzling the philosophical enterprise since at least the 19th century, due to the work of scientific philosophers as Duhem, Mach or Boltzmann. Duhem pioneered in his seminal treaties “The Aim and Structure of Physical Theory” the idea that metaphysical reasoning is parasitical upon scientific account, thus science should abandon the metaphysical kind of explanation (Duhem 1991, pp.3-5).
The background assumptions of contemporary metaphysics of science can be traced back to the aforementioned scientific philosophical tradition. Schrenk provides in the first chapter of the book an historical account of this tradition in order to discover how the background premises have come into being (Schrenk 2016, pp.1-45). I am classifying the assumptions in two distinct groups, by using a couple of intuitive metaphors. I am calling the first stock the toolbox approach, according to which the contemporary metaphysics is either useful, or indispensable for contemporary science and in consequence it should be scientifically-informed. Metaphysical concepts, such as causal power, agency or law of nature, could be useful tools, for explaining how science gets it right in its theories or practices. On the other hand, I am referring to the second pair as the bestiary account, which reinforces the duhemian meta-metaphysical thesis stated above, asserting the hindrance of the metaphysical concerns to the scientific inquiry. The bestiary account urges for the abandonment of the horror metaphysicus from the scientific inquiry.
The distinction is not clear-cut because there are many intermediary nuances between the toolbox and bestiary accounts. For example, it could be an account which shares common ideas from both of them. Perhaps neither the toolbox, nor the bestiary approaches are sets of uniform and homogeneous cluster of theses. Pan-Dispositionalism and Categoricalism could be regarded as toolbox-based metaphysical positions, even if the latter and the former are mutually exclusive theories. I am taking for granted for the present concerns that the purported distinction is unproblematic.
Schrenk’s main aim is to unfold the interrelatedness of dispositions, laws of nature, counterfactuals and causation, whereas the problem of metaphysical dispositions is the unifying theme of his textbook (Schrenk 2016, p. X-XI). Causal powers are regarded as properties which manifest themselves only under very specific conditions. In this particular sense they are ontologically distinct from categorial properties. If a cube of sugar is put in a glass of water, then it dissolves. The former conditional proposition has the following trigger/manifestation metaphysical structure. The property of solubility must meet some specific requirements and background conditions in order for it to obtain (Schrenk 2016). On the other hand, the molecular structure of sugar doesn’t depend from an ontic point of view on the trigger/manifestation conceptual scheme. Sugar’s chemical structure is always obtaining. The main difference between the dispositional and categorial properties could be couched in a modal understanding of their ontologies (Schrenk 2016, pp.66-70)
Dispositions exhibit three distinct features: (1) Non-Observability, (2) Modality and (3) Production (Schrenk 2016, pp.47-52). The bestiary perspective copes with these properties by following an empiricist and reductionist-inspired credo, according to which dispositional properties should be either reduced to observable properties, or to counterfactual statements (Schrenk 2016, pp.45-47). Both disjuncts agree that dispositions have to come under the form of the if/then logical conditional. The bestiary approach relates (1) to (2) by further applying the empiricist dictum to the modality feature. This approach accepts beyond doubt that disposition is a modal-laden metaphysical concept. The modality of causal powers should be, for example, stated under the form of counterfactuals. If the cube of sugar was put in a glass of water, then it would dissolve. The antecedent describes a possible world p, where a cube of sugar is put in water and the consequent describes a possible world q, where the cube actually dissolves. The counterfactual from above says blatantly that p worlds are q worlds (Schrenk 2016, pp.102-112). The bestiary account reduces the modality of disposition to similar counterfactual readings. A somewhat similar move is made to account for (3). Production refers to the responsibility of causal powers, e.g a disposition is regarded as producing and maintaning a certain reaction in particular situations (Schrenk 2016, pp.56-57). The 13-Carbon has probability of 50% to decay. If it decays, it would produce, for examples, such and such effects on the environment. The concept of causation, already present in the third feature, is explained by the bestiary account linking it to previous two strategies.
The toolbox perspective delivers a very different kind of narrative for the explanation of causal powers. Pan-Dispositionalism takes causal powers as irreducible, fundamental and basic features of the world (Schrenk 2016, pp.119-121). (1) is not regarded as a proper problem for the toolbox approach, for this account commits itself to the full-blooded existence of unobservable entities, properties and processes. A similar thing goes for (2). The possible world talk is not a useful device because the primitivist commitment to causal powers doesn’t need a semantics for modality. Perhaps, according to the toolbox view, dispositions are the primitive modal features of the world, and the counterfactual semantics should be reduced to dispositions, not vice-versa, as the bestiary account is demanding (Schrenk 2016, p.121)
On the other hand, the tool box approach seems to require an additional metaphysical commitment to reality of causes in order to provide a powerful explanation of causation and production. Cartwright in her most recent book gives a compelling argument for this point: “A world of Humean features alone (t.n as it is described by the bestiary account) would be a strange under-populated place, devoid of so much that makes up the world we experience. There would be no pushing; no pullings; no teachings or learnings; no smotherings or uncoverings; no eliminatings or restorings; no grating, no choppings, bakings, whiskings, sauteeings, boilings; no beheadings, invadings, executings, enslavings or freeing; no helpings nor hinderings; electings nor just taking charges” (Cartwright 2018, p.35) To put it other way around, reality or the “dappled world”, according to her artful nature perspective, is a messy arrangement of causes.
A brief review of these
approaches shows that both of them provide interesting insights about the
scientific inquiry and its metaphysical baggage. One thing is sure after
reading Schrenk’s textbook. To paraphrase the kantian dictum, I should say that
without science metaphysics is blind and without metaphysics science is empty.
 I am using causal powers, dispositions and capacities as interchangeable concepts.
 Schrenk examines the meta-metaphysical assumptions of these schools of tought in the epilogue of his book (Schrenk 2016, pp.285-325)
- Cartwright, Nancy (2019), “Nature, the Artful Modeler”, ed.Open Court
- Duhem, Pierre (1991), “The Aim and Structure of Physical Theory”, ed. Princeton University Press
- Quine, Williard von Orman (1966), “Necessary Truth”, from The Ways of Paradox and Other Essays, ed. Harvard University Press, pp.68-78
- Schrenk, Markus (2016), “Metaphysics of science. A Systematic and Historical Introduction”, ed. Routledge Press