Sabrina (Beishi) Hao

In this paper, I explore the relation between actual scientific practice and conceptual interpretation of scientific theories by investigating the particle concept in non-relativistic quantum mechanics (NRQM). On one hand, philosophers have raised various objections against the particle concept within the context of NRQM and proposed alternative ontologies such as wave function realism, Bohmian particles, mass density field, and flashes based on different realist solutions to the measurement problem. On the other hand, scientists continue to communicate, reason, and explain experimental phenomena using particle terms in the relevant regimes.

It has been explicitly argued and, for most of the time, implicitly assumed in the philosophical literature that we do not need to take scientists’ particle talk seriously, and recovering position measurement of particles in our ontological accounts is sufficient to make contact with scientific practice. In this paper, I argue that although scientific discourse does not postulate a uniform and coherent ontology, it nevertheless postulates real properties. Our ontological accounts thus need to recover the various properties associated with the NRQM particle concept in scientific discourse. I show that recovering these particle properties is not trivially achievable by pointing out some particular challenges these revisionary ontologies face in the process.

The referential status of unobservable scientific terms has been at the center of the tension between scientific realism and theory change. On the one hand, descriptivist theories cannot account for referential success across theory changes; on the other hand, the causal theory of reference is accused of making reference too easy and fails to account for referential failure. Building on the works of Nola (1980) and Psillos (1999; 2012), I develop a refined version of the hybrid causal descriptivist theory in this paper. I first show how an exactly true causal description that survives through theory change is possible if we include the relevant experimental conditions and contexts. I then argue that the meaning of a scientific term fixed through a causal description consists of the referent only, which allows us to account for the complex linguistic behavior in the scientific community. At last, I draw from Donnellan’s (1966) distinction between attributive use and referential use of definite description to account for scientific terms that are introduced without being associated with any phenomenon.

The ontological debate in relativistic quantum field theory (RQFT) has primarily focused on whether the formalism of the theory supports a particle interpretation or a field interpre- tation. In light of several no-go results, many philosophers of physics believe that RQFT is not fundamentally a theory about particles. In this paper, I consider the ontological inter- pretation of RQFT within the broader framework of scientific realism, and I conclude that we should admit particles into our ontology, even if they are emergent.

I begin my analysis with the assumption that an ontological interpretation of RQFT must be coherent with some version of scientific realism. Since all versions of scientific realism face the challenge posed by theory change, I argue that an ontological interpretation of RQFT must go beyond theory interpretation and attend to the details of experimental success. I provide two arguments for including particles in our ontology. First, a particle concept must be postulated in order to realistically interpret the experimental setups that confirm RQFT. Second, a particle concept must be postulated to explain the scientific success of particle physics throughout its history.

1. A paper on the difference between theoretical evidence and experimental evidence for an entity's existence. Theoretical evidence for an entity’s existence is that the entity is postulated in the theoretical explanation of an experimental phenomenon; experimental evidence for an entity’s existence is that the entity is postulated in the direct causal explanation of an experimental phenomenon. I maintain that there is an epistemic distinction between committing to quarks because they are postulated in the theoretical explanation of proton mass and committing to electrons because they are postulated in the causal explanation of a cloud chamber (i.e., an electron detector). 

2. A paper on how an unobservable natural kind term's reference gets fixed when scientists come to the consensus that its existence is confirmed. Confirmation is achieved if the set of evidence is strong enough to rule out all other possible theoretical hypotheses and only one scientific explanation of the observed phenomena is confirmed. The reference is thus fixed through some crucial causal properties postulated in that explanation.

3. A paper proposing a novel definition for emergent entities based on the ontological distinction between state-independent and state-dependent properties. State-independent properties are the properties that are carried by the bearers all the time regardless of what state the bearers are in. In contrast, state-dependent properties are the ones that are carried by the bearers only when the bearers are in some specific states. Following this, I define emergent entities as the ones that 1) can be seen as specific states of some other entities and 2) carry a set of state-independent properties crucial to scientific explanation that are not state-independent for other entities. 

4. A paper proposing a revised version of structural realism reconciling with traditional scientific realism. For non-fundamental levels, even if we grant that we should only commit ourselves to the structural content of our theories, this structural content already instantiates emergent entities (just like the structure of the fields instantiates particles). 

In Dao De Jing, the most important work of Daoism, Lao Zi considers the common-sensical intuition of carving nature in a binary way: if there is a concept of beauty then there is a concept of ugliness (non-beauty); if there is a concept of goodness then there is a concept of badness (non-goodness). This phenomenon also occurs in Western logic and can be related to the set-theoretic representation of properties: naively, for every property P, there exists a set whose members are all and only the objects that satisfy P and a set whose members are all and only the objects that do not satisfy P. This binary nature in Western logic leads to famous paradoxes, including Russell’s paradox in set theory.

Lao Zi suggests that we should see the opposite beings and properties as co-existent and complementary to each other. All beings in the binary world that we observe are derived from Oneness, and Oneness is derived from Nonbeing—Dao. If we consider the concept of Oneness in a set-theoretic framework, it should be represented by the universal set which includes itself. Most importantly, Oneness is not subjected to paradoxes because the concepts of truth, negation, and contradiction are all derived concepts and cannot be attributed to the descriptions of Oneness. Oneness is metaphysically prior to all binary and negatable concepts. In this way, I offer a new perspective on some key ideas in Dao De Jing by situating them in the framework of Western logic. 

In 1922, Fung Yu-lan published a famous paper titled "Why China Has No Science", in which he argued that "what keeps China back is that she has no science", but that "China has no science, because according to her own standard of value she does not need any." In this paper, I compare the verdicts on values of science in Daoism and Western analytic tradition by tracing the source of the difference to their different metaphysical pictures.