Thought Experiment, Ibn Sina and Descartes

A thought experiment is a method in which a specific situation, event, or hypothesis is mentally constructed to test it, in cases where direct experimental or observational means are unavailable. This approach allows for the testing of existing knowledge or principles through a hypothetical scenario. Thought experiments have been employed for various purposes in science, philosophy, and logic, and have long been among the conceptual tools of numerous philosophers and scientists throughout history.

In classical Islamic philosophy, one of the earliest examples of a thought experiment is attributed to Ibn Sina (980–1037). Ibn Sina’s thought experiment, known as the “flying man,” was designed to demonstrate that human selfhood can retain awareness even independent of the body. In this experiment, one is asked to imagine a person born blind and deaf, suspended in midair with no sensory contact whatsoever. In such a condition, despite receiving no information from the external world, the person would still be conscious of their own existence. According to Ibn Sina, this indicates that the soul (nafs) is a substance distinct from the body and that selfhood cannot be reduced to sensory experience.

Ibn Sina’s thought experiment occupies an original position within the context of the Aristotelian and Neoplatonic philosophical traditions and kalam debates of his time. While Aristotle defined the soul as the form of the body, Neoplatonism emphasized the soul’s independence from the body. Ibn Sina synthesized this heritage with his own metaphysical and epistemological framework to draw attention to the soul’s dimension of self-awareness. His approach, by positing a self-consciousness independent of sensory data, influenced subsequent centuries both in the Islamic world and in the West.

In Western philosophy, René Descartes (1596–1650) employed thought experiments within the framework of methodological skepticism. Descartes’s most famous thought experiment is the “evil demon” hypothesis. According to this hypothesis, all our sensory experiences might be deceptive, and even the entirety of reality could be manipulated by a powerful and deceitful entity. This assumption necessitates the questioning of all beliefs in order to attain certain knowledge. In this radical process of doubt, Descartes arrived at the proposition “I think, therefore I am” (cogito, ergo sum), establishing the subject’s undeniable existence as foundational knowledge.

Although Ibn Sina’s and Descartes’s thought experiments differ in purpose and context, both emphasize the centrality of self-awareness. Ibn Sina’s “flying man” scenario argues that self-awareness remains possible even when completely isolated from empirical conditions. Descartes’s method, by contrast, rejects the reliability of the senses and grounds certainty solely in the act of thinking itself. Both approaches open the door to the idea of a mental entity independent of the body.

Historically, the fact that Ibn Sina’s thought experiment was developed approximately six centuries before Descartes’s demonstrates that the concept of self-awareness has a deep tradition outside Western philosophy. Scholars have offered differing views on whether the similarities between the two thinkers result from direct influence or independent discovery. However, it is clear that both thought experiments remain important references in epistemological analyses and debates in the philosophy of mind.

Today, the “flying man” experiment is still used in modern consciousness research to understand the phenomenological nature of subjective experience and the continuity of selfhood. Similarly, Descartes’s skeptical method is regarded as a valid tool in contemporary epistemology for examining the relationships between knowledge, truth, and belief. Thought experiments, as illustrated by both Ibn Sina and Descartes, retain their significance not merely as philosophical techniques but as a means of exploring the limits and possibilities of the human mind.