Life on the Edge
I am a member of the interdisciplinary project "Life on the Edge," led by physicists Jim Al-Khalili and Andrea Rocco at the University of Surrey, joined by collaborators at Bristol, Surrey, Oxford, UCLA, and Arizona State, and funded by a $3 million grant from the John Templeton Foundation. Here is the official project description: "In this project we will investigate the complex interrelationship between the nature of time and the distinct ways in which the passage of time and quantum physics manifest in inanimate objects compared to living organisms. Expanding the theoretical and philosophical frameworks used to understand the ‘arrow of time’ and reversibility, the project will encompass three theoretical investigations, an experimental approach using live cells, and a philosophical exploration of the deeper meanings of time." My focus will be on the relation of quantum ontology and the arrows of time in living systems.
Time's Arrow in a Quantum Universe ["The Wentaculus"]
I have been working on a new project related to time's arrow in a quantum universe. The key idea is that the arrow of time in our universe is crucial for understanding the nature of quantum mechanics and vice versa. I propose that the "fundamental" quantum state of the universe is a special "mixed state," represented not by a wave function but a density matrix, selected by what I call the Initial Projection Hypothesis. I call the whole package "the Wentaculus." The idea was first presented in my 2021 BJPS paper, which won the Popper Prize.
The Wentaculus has several implications:
(1) it unifies time's arrow and quantum ontology in the Humean framework (Noûs, 2020);
(2) it eliminates statistical-mechanical probabilities in the fundamental postulates (in a volume edited by Valia Allori, World Scientific, 2020);
(3) it dissolves the tension between "fundamental nomic vagueness" and "untraceable arbitrariness" of the Past Hypothesis (The Philosophical Review, 2022; a popular version of this article is featured as a cover story in New Scientist);
(4) it sheds light on various notions of empirical equivalence;
(5) it suggests a strongly deterministic interpretation for the many-worlds interpretation of quantum mechanics (in a volume edited by Sara Bernstein and Tyron Goldschmidt, Oxford University Press, 2021; another paper available as a preprint);
(6) it provides a new perspective on the reality of the quantum state, especially in relation to the PBR theorem.
Metaphysics of Quantum Mechanics
I suggest that we should trace various philosophical puzzles of quantum mechanics back to their source--the wave function. First, I clarify how its mathematical representation relates to the physical world. In "An Intrinsic Account of Quantum Mechanics: Progress in Field's Nominalistic Program," I show that the wave function represents four intrinsic relations on physical space-time, uniquely up to certain symmetries. Since my intrinsic account dispenses with any reference to mathematical objects, it extends Field's nominalistic program to the quantum realm. In "Our Fundamental Physical Space: An Essay on the Metaphysics of the Wave Function" (JPhil, 2017), I argue against configuration space realism, the view that physical space-time is "emergent" from the high-dimensional configuration space that the wave function lives on. Emphasizing the roles of dynamics and symmetries, I show that physical space-time is more fundamental than the configuration space. In "Quantum Mechanics in a Time-Asymmetric Universe: On the Nature of the Initial Quantum State" (BJPS, 2018), I show that, by using the Past Hypothesis to pin down a simple and unique quantum state, we discover a new way of thinking about the relationship between the quantum state of the universe and the arrow of time. My proposal leads to a new class of quantum theories that dispense with certain objective probabilities and reconcile Humean supervenience with quantum entanglement. This paper is related to the first project.
Decision Theory and Infinite Values
I have been working, in collaboration with Daniel Rubio, on the foundations of decision theory and analyzing the paradoxes related to infinities such as Pascal’s Wager and the Pasadena Game (Nover and Hájek, 2004). In our paper “Surreal Decisions” (PPR, 2018), we propose a decision theory framed entirely in John Conway's (1974) surreal numbers. By using surreal numbers as the values of the utility function and the probability function, we show that many paradoxes of infinite values disappear in finite state spaces. In particular, dominance principles are no longer in conflict with expected utility theory. We are working on a second paper that extends surreal decision theory to the more advanced setting of infinite state spaces, such as the Pasadena Game. As a decision theory that systematically handles infinities and infinitesimals, our surreal theory has applications in value theory, population ethics, and philosophy of religion.
Metaphysics of Mental Qualities
I have another research project about metaphysics of quantities and philosophy of mind. Mental qualities (such as being painful and being conscious) are usually taken to be absolute and monadic. In my paper "Comparativism about the Mind: From Metaphysics of Quantities to the Nature of Mentality," I propose a new hypothesis about the nature of mental qualities: they are fundamentally comparative; for example, being more painful than is more fundamental than being painful. I call this the Comparative Mentality Hypothesis (CMH). CMH is motivated by comparativism about the physical as well as some theories about the mind-body problem. I use color qualities as the main example for CMH, and I provide an axiomatic foundation of color hues in terms of two comparative relations: cyclic-betweenness and cyclic-congruence. They turn out to have the same comparative structure as wave-function phases (Chen 2017a). I draw some consequences from CMH for reductionist physicalism and what David Chalmers (forthcoming) calls micro-idealism. In future work, I will apply CMH to other mental qualities and contrast it with comparativism about subjective probabilities.
Chinese Philosophy
I have two research projects in Chinese philosophy. The first one is at the intersection of classical Chinese philosophy and meta-ethics. In my paper “A Hybrid Voluntarist Interpretation of Xunzi,” I display tensions in the notions of xin (heart/mind), li (rituals), and dao (order) in the work of Xunzi, a prominent early Confucian philosopher, and I draw on Ruth Chang’s (2013a, 2013b) meta-ethical theory of hybrid voluntarism to help resolve these tensions. The second project is about issues related to the “Needham Question” about the history of science in China. I explore the connections between concepts of laws of nature with the concept of Dao in Chinese philosophy.
I am a member of the interdisciplinary project "Life on the Edge," led by physicists Jim Al-Khalili and Andrea Rocco at the University of Surrey, joined by collaborators at Bristol, Surrey, Oxford, UCLA, and Arizona State, and funded by a $3 million grant from the John Templeton Foundation. Here is the official project description: "In this project we will investigate the complex interrelationship between the nature of time and the distinct ways in which the passage of time and quantum physics manifest in inanimate objects compared to living organisms. Expanding the theoretical and philosophical frameworks used to understand the ‘arrow of time’ and reversibility, the project will encompass three theoretical investigations, an experimental approach using live cells, and a philosophical exploration of the deeper meanings of time." My focus will be on the relation of quantum ontology and the arrows of time in living systems.
Time's Arrow in a Quantum Universe ["The Wentaculus"]
I have been working on a new project related to time's arrow in a quantum universe. The key idea is that the arrow of time in our universe is crucial for understanding the nature of quantum mechanics and vice versa. I propose that the "fundamental" quantum state of the universe is a special "mixed state," represented not by a wave function but a density matrix, selected by what I call the Initial Projection Hypothesis. I call the whole package "the Wentaculus." The idea was first presented in my 2021 BJPS paper, which won the Popper Prize.
The Wentaculus has several implications:
(1) it unifies time's arrow and quantum ontology in the Humean framework (Noûs, 2020);
(2) it eliminates statistical-mechanical probabilities in the fundamental postulates (in a volume edited by Valia Allori, World Scientific, 2020);
(3) it dissolves the tension between "fundamental nomic vagueness" and "untraceable arbitrariness" of the Past Hypothesis (The Philosophical Review, 2022; a popular version of this article is featured as a cover story in New Scientist);
(4) it sheds light on various notions of empirical equivalence;
(5) it suggests a strongly deterministic interpretation for the many-worlds interpretation of quantum mechanics (in a volume edited by Sara Bernstein and Tyron Goldschmidt, Oxford University Press, 2021; another paper available as a preprint);
(6) it provides a new perspective on the reality of the quantum state, especially in relation to the PBR theorem.
Metaphysics of Quantum Mechanics
I suggest that we should trace various philosophical puzzles of quantum mechanics back to their source--the wave function. First, I clarify how its mathematical representation relates to the physical world. In "An Intrinsic Account of Quantum Mechanics: Progress in Field's Nominalistic Program," I show that the wave function represents four intrinsic relations on physical space-time, uniquely up to certain symmetries. Since my intrinsic account dispenses with any reference to mathematical objects, it extends Field's nominalistic program to the quantum realm. In "Our Fundamental Physical Space: An Essay on the Metaphysics of the Wave Function" (JPhil, 2017), I argue against configuration space realism, the view that physical space-time is "emergent" from the high-dimensional configuration space that the wave function lives on. Emphasizing the roles of dynamics and symmetries, I show that physical space-time is more fundamental than the configuration space. In "Quantum Mechanics in a Time-Asymmetric Universe: On the Nature of the Initial Quantum State" (BJPS, 2018), I show that, by using the Past Hypothesis to pin down a simple and unique quantum state, we discover a new way of thinking about the relationship between the quantum state of the universe and the arrow of time. My proposal leads to a new class of quantum theories that dispense with certain objective probabilities and reconcile Humean supervenience with quantum entanglement. This paper is related to the first project.
Decision Theory and Infinite Values
I have been working, in collaboration with Daniel Rubio, on the foundations of decision theory and analyzing the paradoxes related to infinities such as Pascal’s Wager and the Pasadena Game (Nover and Hájek, 2004). In our paper “Surreal Decisions” (PPR, 2018), we propose a decision theory framed entirely in John Conway's (1974) surreal numbers. By using surreal numbers as the values of the utility function and the probability function, we show that many paradoxes of infinite values disappear in finite state spaces. In particular, dominance principles are no longer in conflict with expected utility theory. We are working on a second paper that extends surreal decision theory to the more advanced setting of infinite state spaces, such as the Pasadena Game. As a decision theory that systematically handles infinities and infinitesimals, our surreal theory has applications in value theory, population ethics, and philosophy of religion.
Metaphysics of Mental Qualities
I have another research project about metaphysics of quantities and philosophy of mind. Mental qualities (such as being painful and being conscious) are usually taken to be absolute and monadic. In my paper "Comparativism about the Mind: From Metaphysics of Quantities to the Nature of Mentality," I propose a new hypothesis about the nature of mental qualities: they are fundamentally comparative; for example, being more painful than is more fundamental than being painful. I call this the Comparative Mentality Hypothesis (CMH). CMH is motivated by comparativism about the physical as well as some theories about the mind-body problem. I use color qualities as the main example for CMH, and I provide an axiomatic foundation of color hues in terms of two comparative relations: cyclic-betweenness and cyclic-congruence. They turn out to have the same comparative structure as wave-function phases (Chen 2017a). I draw some consequences from CMH for reductionist physicalism and what David Chalmers (forthcoming) calls micro-idealism. In future work, I will apply CMH to other mental qualities and contrast it with comparativism about subjective probabilities.
Chinese Philosophy
I have two research projects in Chinese philosophy. The first one is at the intersection of classical Chinese philosophy and meta-ethics. In my paper “A Hybrid Voluntarist Interpretation of Xunzi,” I display tensions in the notions of xin (heart/mind), li (rituals), and dao (order) in the work of Xunzi, a prominent early Confucian philosopher, and I draw on Ruth Chang’s (2013a, 2013b) meta-ethical theory of hybrid voluntarism to help resolve these tensions. The second project is about issues related to the “Needham Question” about the history of science in China. I explore the connections between concepts of laws of nature with the concept of Dao in Chinese philosophy.