Epigraph:

And they ask you concerning the soul. Say, ‘The soul is by the command of my Lord; and of the knowledge thereof you have been given but a little.’ (Al Quran 17:85)

Written and collected by Zia H Shah MD, Chief Editor of the Muslim Times

If my articles are boring to you, it may be that you need to read more of them, as was suggested by John Cage, one of the most influential American composers of the 20th century, “If something is boring after two minutes, try it for four. If still boring, then eight. Then sixteen. Then thirty-two. Eventually one discovers that it is not boring at all.”

Philosophical thought experiments are critical tools for understanding the hard problem of consciousness. These imaginative scenarios aim to isolate and highlight the distinctions between physical processes and subjective experiences, demonstrating why consciousness cannot be reduced to mechanistic explanations. Below are some of the most influential examples:

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Philosophical Zombies

The “philosophical zombie” is a cornerstone thought experiment popularized by David Chalmers. A philosophical zombie is a hypothetical being indistinguishable from a human in all physical and functional respects but lacking subjective experience. For instance, such a zombie would respond to stimuli, engage in conversations, and exhibit behaviors identical to a conscious human, yet it would have no inner life—it would not feel anything.

Chalmers uses zombies to argue that consciousness cannot be fully explained by physical facts. He contends that the very conceivability of zombies implies that consciousness is non-physical. As he famously states:

“We can coherently conceive of a world that is physically identical to ours but in which there is no consciousness. This suggests that consciousness is not logically entailed by the physical facts.”

Critics like Daniel Dennett challenge this notion, arguing that the concept of a zombie depends on an illusory intuition that overstates the distinction between physical processes and subjective experience. Dennett dismisses the thought experiment as a “philosophical trick,” emphasizing that any being functionally identical to a human must necessarily have consciousness. He describes this as the “zombie hunch,” arguing that the intuition behind it is misguided.

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Mary’s Room (The Knowledge Argument)

Proposed by philosopher Frank Jackson, the Mary’s Room thought experiment challenges physicalist accounts of consciousness by illustrating the limitations of physical knowledge. Mary is a neuroscientist who knows everything there is to know about color vision, including the physical and functional properties of light and the brain’s responses. However, she has lived her entire life in a black-and-white room and has never seen color.

The pivotal moment comes when Mary steps out of the room and sees the color red for the first time. Jackson argues that in this moment, Mary gains new knowledge—specifically, the qualia of seeing red. This knowledge could not be obtained through her physical studies, suggesting that physicalism is incomplete.

Chalmers cites Mary’s Room as a compelling demonstration of the explanatory gap between physical processes and subjective experience. However, some philosophers, including Paul Churchland and Patricia Churchland, argue that Mary’s newfound understanding is better explained as an acquisition of a new ability (e.g., imagining red) rather than knowledge of a new fact. This interpretation aligns with physicalist accounts.

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What Is It Like to Be a Bat?

In his seminal 1974 essay, Thomas Nagel explores the fundamentally subjective nature of consciousness through the example of a bat. Bats navigate their environment using echolocation, a sensory mode entirely alien to humans. Nagel asks, “What is it like to be a bat?” He argues that, even with perfect physical knowledge of a bat’s brain and behavior, we cannot fully comprehend its subjective experience.

Nagel’s argument underscores the distinction between objective facts (accessible through scientific investigation) and subjective experiences (accessible only to the experiencing subject). He concludes that consciousness resists reduction because it inherently involves a “point of view.”

This thought experiment remains one of the most cited arguments for the uniqueness of subjective experience. Critics, like Daniel Dennett, argue that Nagel overstates the problem, suggesting that advances in neuroscience and cognitive modeling could eventually bridge this gap.

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The Inverted Spectrum

The inverted spectrum thought experiment questions whether we can ever truly understand another person’s subjective experiences, even if their behavior and physical responses appear identical to our own. For example, two individuals might label the same object as “red,” but one might perceive the color we know as green. This inversion of subjective experience would remain undetectable from external observation.

This scenario highlights the difficulty of correlating physical processes with subjective experiences. It suggests that qualia—the raw feels of experience—are private and inaccessible to others. As with the philosophical zombie argument, the inverted spectrum challenges the assumption that physicalism can fully account for consciousness.

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The Explanatory Gap

Joseph Levine’s notion of the explanatory gap ties these thought experiments together. He argues that even if we achieve a complete scientific understanding of the brain, we will still lack an explanation for why physical processes give rise to subjective experience. Levine writes:

“There is a gap between our understanding of the physical processes and our understanding of the phenomenal properties they give rise to.”

This gap, illustrated vividly by the thought experiments, serves as the conceptual foundation for the hard problem of consciousness.

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Concluding Thoughts on Philosophical Thought Experiments

These thought experiments illustrate why consciousness is uniquely resistant to reductive explanations. While critics argue that these scenarios rely on intuitions that might be overturned by scientific progress, they remain central to philosophical discussions of the hard problem. By framing consciousness as an irreducible phenomenon, they compel us to reconsider the limits of physicalist explanations and explore alternative frameworks for understanding the mind.