This paper argues that the physics of condensed matter cannot be fully reduced to the supposedly fundamental quantum mechanical theory for all the atoms of which the system consists. In fact, there are many reasons to reject the idea that the world of physics is causally closed with everything being determined bottom-up by fundamental microscopic laws. This is illustrated by considering how condensed-matter theory is done in practice. It is never done by starting with a microscopic theory for the interaction of all the atoms of the system. Instead, approximations, plausible assumptions, intuitive models, and phenomenological theories are used to mathematically describe and explain the properties of systems that consist of a macroscopic number of particles. I argue that this is not merely a matter of convenience, but that there are fundamental and qualitative differences or even contradictions between the microscopic theory and the theory that is used in practice. The paper includes a list of arguments in favor of strong emergence and top-down causation within the realm of physics, and a response to several widespread objections against this view.
This paper argues that the physics of condensed matter cannot be fully reduced to the supposedly fundamental quantum mechanical theory for all the atoms of which the system consists. In fact, there are many reasons to reject the idea that the world of physics is causally closed with everything being determined bottom-up by fundamental microscopic laws. This is illustrated by considering how condensed-matter theory is done in practice. It is never done by starting with a microscopic theory for the interaction of all the atoms of the system. Instead, approximations, plausible assumptions, intuitive models, and phenomenological theories are used to mathematically describe and explain the properties of systems that consist of a macroscopic number of particles. I argue that this is not merely a matter of convenience, but that there are fundamental and qualitative differences or even contradictions between the microscopic theory and the theory that is used in practice. The paper includes a list of arguments in favor of strong emergence and top-down causation within the realm of physics, and a response to several widespread objections against this view.
Abstract Even though physicists often claim that their theories can, in principle, be reduced to the supposedly most fundamental theory, which is quantum physics, a look at how physics is practiced reveals that this reduction is almost never performed. Instead, effective models are built that include various types of contextual information and that are often incompatible with the supposedly fundamental theory. The phenomena described by these models can be characterized as contextually emergent. This chapter illustrates contextual emergence by means of examples from different fields of physics. In quantum physics, explanations of the measurement process require the assumption of a classical context that specifies the observable being measured and that induces the measurement event. In condensed matter theory, we find many types of quasiparticles that can only exist due to the solid that embeds them and the structure of which determines the properties of the quasiparticles. In thermodynamics, state variables such as the pressure and temperature of a system are given by its environment, and its phase transitions are triggered by changes in the environment. In the early universe, the degrees of freedom and the density and temperature determine the types of particles that are found in the universe. Later, the overall properties of the universe determine whether matter can condense to form stars. From all this it follows that processes and descriptions at different scales are equally important in physics. There are even contextual influences from outside physics. The chapter will thus conclude that physics is not causally closed.
Since its inception, the intricate mathematical formalism of quantum mechanics has empowered physicists to describe and predict specific physical events known as quantum processes. However, this success in probabilistic predictions has been accompanied by a profound challenge in the ontological interpretation of the theory. This interpretative complexity stems from two key aspects. Firstly, quantum mechanics is a fundamental theory that, so far, is not derivable from any more basic scientific theory. Secondly, it delves into a realm of invisible phenomena that often contradicts our intuitive and commonsensical notions of matter and causality. Despite its notorious difficulties of interpretation, the most widely accepted set of views of quantum phenomena has been known as the Copenhagen interpretation since the beginning of quantum mechanics. According to these views, the correct ontological interpretation of quantum mechanics is incompatible with ontological realism in general and with philosophical materialism in particular. Anti-realist and anti-materialist interpretations of quantum matter have survived until today. This paper discusses these perspectives, arguing that materialistic interpretations of quantum mechanics are compatible with its mathematical formalism, while anti-realist and anti-materialist views are based on wrong philosophical assumptions. However, although physicalism provides a better explanation for quantum phenomena than idealism, its downward reductionism prevents it from accounting for more complex forms of matter, such as biological or sociocultural systems. Thus, the paper argues that neither physicalism nor idealism can explain the universe. I propose then a non-reductionistic form of materialism called inclusive materialism. The conclusion is that the acknowledgment of the qualitative irreducibility of ontological emergent levels above the purely physical one does not deny philosophical materialism but enriches it.
The nature of emergence of complexity out of the underlying physics is a key issue in understanding the world around us (1). Genuine emergence can be claimed (2⇓–4) to depend on top-down causation, which enables higher emergent levels to direct the outcomes of causation at lower levels to fulfill higher-level causal requirements; for example, the needs of heart physiology at the systems level determine gene expression at the cellular level via gene regulatory networks (5) (Fig. 1). However, the idea of top-down causation has been denied by a number of commentators (e.g., refs. 6 and 7). The paper by Aharonov et al. (8) makes a strong contribution to this debate by giving quantum physics examples where top-down causation manifestly occurs. This physics result has strong implications for the philosophical debate about whether strong emergence is possible. Indeed, it gives specific examples where it occurs in a remarkably strong form.
Fig. 1.
Bottom-up and top-down causation from the quantum level up to the organism level and down again. Adapted with permission of Royal Society, from ref. 5; permission conveyed through Copyright Clearance Center, Inc.
Now, the word “causation” is regarded with suspicion by many philosophers of science, so to characterize what is happening one can perhaps rather use a number of different descriptions such as “whole–part constraint” or “top-down realization.” The key point remains the same, that higher levels can influence lower-level outcomes in many ways, and hence explain how strong emergence is possible. This occurs across science in general, and in physics in particular (3, 4). The latter point …
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Ever since the advent of quantum mechanics, it has been clear that the atoms composing matter do not obey Newton's laws. Instead, their behavior is described by the Schroedinger equation. Surprisingly though, until recently, no clear explanation was given for why everyday objects, which are merely collections of atoms, are observed to obey Newton's laws. It would seem that, if quantum mechanics explains all the properties of atoms accurately, they, too, should obey quantum mechanics. This reasoning led some scientists to believe in a distinct macroscopic, or ``big and complicated,'' world in which quantum mechanics fails and classical mechanics takes over, although there has never been experimental evidence for such a failure. Even those who insisted that Newtonian mechanics would somehow emerge from the underlying quantum mechanics as the system became increasingly macroscopic were hindered by the lack of adequate experimental and theoretical tools. In the last decade, however, this quantum-to-classical transition has become accessible to experimental study and quantitative description, and the resulting insights are the subject of this article.
This article examines the need for a comprehensive theory that explains the creation of the universe and the enigmatic behaviours observed in quantum particles. Recent advancements in quantum physics have revealed phenomena in the microscopic and macroscopic realms that challenge conventional explanations based solely on natural laws. This article introduces an argument centred on the concept of “presence of metaphysics in physics” as a means to provide a plausible account for the improbable existence of the universe and the mechanics of the space-time continuum. By incorporating ontological principles in classical physics and quantum mechanics, this proposed model sheds light on the origins of natural laws while also considering the mysterious balance and intricacies observed in micro and macrocosms. Moreover, this article argues that a mere succession of random events guided by mathematical probabilities cannot adequately establish and govern the natural laws that appear to have arisen with the aim of fostering life within the universe.
Quantum mechanics arguably provides the best evidence we have for strong emergence.Entangled pairs of particles apparently have properties that fail to supervene on the properties of the particles taken individually.But at the same time, quantum mechanics is a terrible place to look for evidence of strong emergence: the interpretation of the theory is so contested that drawing any metaphysical conclusions from it is risky at best.I run through the standard argument for strong emergence based on entanglement, and show how it rests on shaky assumptions concerning the ontology of the quantum world.In particular, I consider two objections: that the argument involves Bell's theorem, whose premises are often rejected, and that the argument rests on a contested account of parts and wholes.I respond to both objections, showing that, with some important caveats, the argument for emergence based on quantum mechanics remains intact.