Quantum Mechanics and Metaphysics

The following essay explores the philosophical issues of quantum mechanics that arise regarding consciousness, determinism, and reality. After evaluating different approaches, it was found that the many-worlds interpretation acts as the best approach to quantum physics from the perspective of metaphysics, the branch of philosophy which deals with deep questions relating to topics such as reality, the relationship between mind and matter, and God.
Arguably one of the most ground-breaking achievements in physics occurred in the 1920s with the discovery of quantum mechanics. Initially put forward by Max Planck, quantum mechanics was further developed by physicists such as Werner Heisenberg, Erwin Schrödinger, and Richard Feynman. Quantum physics describes the way subatomic particles behave, claiming that a subatomic system is in a superposition before it is measured or observed. That is, the system exists as a linear combination of several distinct possible states before it collapses into a single state once measured. The isolated state can then be expressed by a single wave function, a mathematical equation that characterizes the system (e.g. its position, spin, momentum) using probabilities. This description of quantum mechanics is known as the Copenhagen interpretation, and can be better understood through Schrödinger’s famous thought experiment: suppose that a cat is placed in a box with a flask that has a 50% chance of releasing poison after a certain time. Quantum physics implies that the cat will be simultaneously both alive and dead (superposed state). Only after an observer opens the box and checks, the cat’s superposition will collapse into one state – either dead or alive.

Figure 1: Schrödinger’s cat
Despite quantum theory being the most accurate description of the behaviour of subatomic particles that we currently possess, it is highly counterintuitive as it introduces an element of randomness and uncertainty into the scientific framework. The paradigm shift caused by quantum physics affected not only the field of physics, but also the way in which we view the world in general, and thus naturally raised fundamental questions in philosophy, particularly in metaphysics. The most significant ones being: what do quantum models suggest about the nature of reality, especially about God, and humans’ perception of reality? Can consciousness explain wave function collapses? Additionally, what does quantum physics imply about causal determinism, a concept that suggests all events are necessitated (and thus can be predicted) by precedent events and conditions? Asking metaphysical and other philosophical questions such as these is imperative to the development of physics, and ultimately, to the general understanding of the universe as more of our reality is understood.
The Copenhagen Interpretation and Consciousness
According to the Copenhagen interpretation, when superposed particles interact with other subatomic particles, their states become entangled with each other and become part of a larger superposed system. The system collapses into a definite wave function only once it encounters a determinate property, which is one that does not become entangled with the superposed system. The “determinate property” is often regarded as a measurement, or observation. However, the Copenhagen interpretation does not state what constitutes an observation or measurement, thus causing the philosophical issues to arise. This is known as the measurement problem. An alternative theory of a determinate property to resolve the measurement problem is consciousness: the quality of being aware of internal and external existence. The theory of consciousness acting as the determinate property, referred to simply as consciousness theory, can be easily justified, although it does not hold. By nature, one cannot conceive of superposed conscious states – a person cannot be, for example, simultaneously conscious and unconscious. The philosophical implications of consciousness theory lie in its connection to Cartesian dualism, the view that the mind and body exist as separate entities; mental processes are purely nonphysical and the body cannot think. The theory heavily supports and relies on the nonphysical mind existing as something that consciousness manifests in. This is so that consciousness is able to act as a property that can independently interfere with physical processes (the quantum system), since it is unable to become entangled with it due to the fact that it is nonphysical. To better understand the theory, consciousness can be interpreted as being similar to electromagnetic fields, which are nonphysical yet still concrete and independent constituents of the physical world/reality that interact with physical entities. In the same way, consciousness is a nonphysical property that inheres in beings and is able to trigger collapses in superposed quantum systems by refusing to become entangled with it. There are, however, clear inconsistencies in the argument for consciousness theory. For example, it would be difficult to explain how severe brain damage can lead to the loss of consciousness if one’s conscious state is purely nonphysical. Additionally, consciousness is still far too vague and no more concrete than measurement. Where do we draw the border on what has consciousness and what does not? According to the argument, scientific instruments must also possess consciousness as they are able to collapse quantum systems, but they likely do not possess awareness of internal existence, which defies the definition of consciousness. Hence, it seems that consciousness is not a good resolution to the measurement problem due to its vague nature.
Quantum Indeterminism
One of the main philosophical changes that quantum mechanics introduced into science was regarding causal determinism. Quantum behaviour is random, not subject to prior causes, and outcomes cannot be predicted all due to empirical limitations (e.g. the observer effect and Heisenberg\’s uncertainty principle, where one even theoretically cannot simultaneously determine the velocity and position of a particle). Hence, nature, at its core, is believed to be indeterministic. This contradicts previous scientific belief that all characteristics, meaning both velocity and position, of any given situation can be accurately predicted using sets of classical laws and equations. The argument that the universe is indeterministic is strong in the sense that pure randomness, as arises in quantum mechanics, is truly incompatible with determinism. One can argue, however, that the concept is also rather futile and self-contradictory; if the causality of events in the universe cannot be accurately understood by science due to empirical limitations and our forever insufficient computational power (as we would have to consider all information that exists in the universe), then science cannot be used to undermine nor prove determinism. Science seeks as much determinism and certainty as possible, but it is impossible to either prove or falsify, at least from the point of view of quantum mechanics, that our universe is deterministic for the aforementioned reasons.
Many-Worlds Interpretation
In addition to the Copenhagen interpretation, physicists have developed other models to describe quantum phenomena. A more skeptical but still widely acknowledged approach is the many-worlds interpretation, a deterministic theory for the universe in which wave function collapses do not occur. Instead, all possible states of the superposed system will physically come to exist simultaneously in parallel worlds. In the case of Schrödinger’s cat, this implies that, after observation, the cat will come to exist in an alive state in one reality, as well as in a dead state in another.

Figure 2: Schrödinger’s cat and the many-worlds interpretation
While it is philosophically controversial, it is a fully plausible theory and has also appeared in other areas of physics, for example string theory. Moreover, it could provide an explanation for a problem present in science, religion, and philosophy that is significant and difficult to counter-argue, until now. To explain how life is able to exist in our universe, fundamental physical constants must be “fine-tuned” to incredibly precise values. If these constants, for example the universal constant G, were even slightly different, the universe would be unable to support life. The fine-tuning argument suggests that the chances of life are therefore so improbable that one can conclude it was the work of a higher being. The many-worlds interpretation, however, completely undermines this argument. If there are an infinite number of universes, the local reality perhaps just happens to exist in one where the exact conditions for life are correct, thus deeming the need for a creator unnecessary. The many-worlds interpretation is a better model than triggered-collapse models due to it being able to resolve almost all paradoxes in quantum mechanics, especially the previously mentioned issues of measurement and indeterminism. The many-worlds theory can explain why the universe appears to be indeterministic for observers, and naturally eliminates the measurement problem as the theory does not require collapses.
Perception of Reality
Another philosophical issue of quantum theory that should be recognized is humans’ perception of reality. Due to the observer effect, the instruments one uses to measure a quantum system necessarily disturbs and alters the outcome. The most famous example is the double-slit experiment, where electrons are shot through two slits. When unobserved, the electrons behave as waves as seen from their interference pattern; when the experiment is observed, the electrons can only be seen going through one slit at a time, acting as particles. Thus, one is at a fundamental level never able to precisely perceive reality as it truly is, since it is altered once observed. This raises the question of what an “actual” reality would look like when there are no observers, although the exact extent to which the observer effect alters reality is unknown.
In conclusion, quantum mechanics has fundamentally rewritten humanity’s understanding of the universe in terms of physics. With paradigm shifts within any science, however, arises conflicts and solutions to both old and new philosophical questions. Quantum physics is revolutionary from the aspect of how different it is to classical physics; it has introduced a new and unexpected element of uncertainty into science. Uncertainty heavily affects how the universe is perceived, as well as the local world. It suggests that the universe is indeterminate, as the randomness that is exhibited by subatomic particles does not allow outcomes to be predicted. However, it is important to note that this is due to limitations in empirical observation, which should then make quantum mechanics an invalid attempt to justify indeterminism. Due to this observer effect, one is unable to directly observe a quantum system without altering the outcome. At a large scale, this could suggest that the way in which we perceive reality significantly differs from how it may be without observers. A possible solution to these issues is the no-collapse many-worlds interpretation, where multiple parallel universes exist. It preserves determinism, as well as solves the fine-tuning problem. The measurement problem that comes with standard collapse theories, such as the Copenhagen interpretation, would also be naturally eliminated instead of having to seek for an explanation via the concept of consciousness. The theory regarding consciousness, however, effectively demonstrates how the fields of philosophy and physics are intertwined and dependent on one another. Through philosophy, humans are able to find possible solutions to physical problems (consciousness solution to measurement problem); through physics we are able to discover new insights to the universe, reality, and existence (consciousness theory allows mind-body dualism). Quantum mechanics is a sophisticated physics theory with elaborate mathematics, but its full implications can only be known once the philosophical questions are answered.
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Image sources:

  1. Unknown owner. https://theconversation.com/quantum-philosophy-4-ways-physics-will-challenge-your-reality-150175 Accessed 28.6.2021. Unknown owner.
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