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Why Physics Cannot Be a Theory of Everything | Thomas Nagel
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Modern physics' success came from excluding subjective experience, leaving consciousness as an unsolvable problem that challenges the idea of a "theory of everything."
Key Insights
Physics' success in the 17th century was due to excluding mental aspects like color, taste, and intention, focusing solely on measurable, spatio-temporal properties.
Daniel Dennett's view is that consciousness is primarily a way to attribute and predict behavior, reducible to physical causes and functional organization.
Nagel posits that any comprehensive description of reality must account for conscious experience, not treat it as a mere byproduct or an irrelevant artifact.
The evolutionary explanation of consciousness faces a challenge: if materialism is insufficient to explain irreducible subjectivity, then a purely materialist evolutionary account may also fail.
Despite a boom in consciousness studies, Nagel observes that few theories directly address how subjective experience arises from physical systems, remaining largely a mystery.
The idea of a "theory of everything" in physics is challenged by the persistent mind-body problem, which requires integrating subjective experience into our understanding of the physical world.
The limitations of objective reality
Thomas Nagel's philosophical journey began with an interest in objective reality and how we can know its properties, initially intending to study physics. However, he found himself drawn to philosophy, particularly the place of mental phenomena within an objective description of the world. Early in his career, the prominent "identity theory" proposed that mental states could be identified with brain states. While Nagel didn't abandon the idea of a material basis for the mind, he realized this approach fundamentally overlooked the subjective aspect of experience – what it is *like* to be a conscious entity. This led him to believe that any materialist or physicalist account of the mind must acknowledge irreducible subjective aspects that cannot be contained within the framework of physics. This forms the crux of his ongoing philosophical stance on the mind-body problem and the limits of scientific explanation.
Physics' success excluded the subjective
Nagel argues that the very success of modern physics stems from its deliberate exclusion of subjective experience. The scientific revolution, spearheaded by figures like Galileo and Descartes, conceptualized objective reality as exclusively quantitative, measurable, and spatio-temporal. Properties that were dependent on human senses, such as color, taste, and smell, along with intentionality or purpose, were stripped away to create a purely physical, mathematical description of the world. This allowed for the development of modern physics but left consciousness, the subjective realm, entirely outside its purview. The enduring mind-body problem, therefore, is the challenge of re-integrating this excluded subjective experience back into our understanding of the physical world that science has so successfully described.
The irreducibility of subjective experience
At the heart of Nagel's argument is the irreducible nature of subjective experience. He uses the thought experiment of what it is like to be a bat – a creature with a radically different sensory apparatus. Our scientific understanding can describe the bat's physical and neurological processes, but it cannot capture the phenomenal *experience* of being a bat. This subjective, first-person perspective, Nagel contends, is a fundamental aspect of consciousness that cannot be fully explained or reduced to objective, third-person scientific descriptions. Any theory of reality that aims to be comprehensive must grapple with this inherent subjectivity, rather than dismissing it as an epiphenomenon or a mere artifact of complex physical processes. The challenge lies in explaining how consciousness emerges from matter without losing its unique qualitative character.
Critique of evolutionary and functionalist explanations
Philosophers like Daniel Dennett propose that consciousness can be understood through a functionalist or behaviorist lens, arguing that mental states are defined by their causal roles and that consciousness is largely an attribution we make to predict behavior. They suggest that this can be explained through an evolutionary trajectory, starting from simple chemical interactions in single-celled organisms to complex brains. Nagel challenges this by asking how such a purely physical and evolutionary story can account for the emergence of irreducible subjectivity if it exists
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Nagel argues that current scientific approaches, particularly physicalism, fail to account for the subjective, 'what it's like' aspect of experience. He believes consciousness has intrinsic subjective qualities that cannot be reduced to purely physical or functional descriptions.
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A distinguished professor of philosophy and law at NYU, known for his influential work on consciousness, the mind-body problem, objectivity, and ethics. His 1974 essay 'What Is It Like to Be a Bat?' redefined discussions on consciousness.
Mentioned implicitly through discussion of philosophical concepts, though not explicitly named.
Along with Galileo, shaped the conception of objective physical reality, contributing to the mind-body problem by separating mind and body.
Mentioned in relation to the identity theory of mind and brain during Nagel's university studies.
Key figure in the scientific revolution whose work established a conception of objective reality as quantifiable and spatio-temporal, excluding mental qualities.
A philosopher whose view on consciousness is described as functionalist/behaviorist, suggesting consciousness is an attribution we make to predict behavior, and which Nagel critiques.
Thomas Nagel's seminal 1974 essay that challenged the prevailing assumption that subjective experience could be fully explained by objective science.
Thomas Nagel's book questioning the sufficiency of neo-Darwinian materialism for explaining the mind.
A book by Thomas Nagel that maps the tensions between the first-person world we experience and the third-person world science describes.
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