The notion of "common sense"—that intuitive grasp of the world most people share—seems straightforward, almost innate. Yet, a historical perspective reveals it is far from static. What one era considered self-evident, another might have dismissed or even found absurd. The evolution of common sense is a story of changing social norms, scientific discovery, and philosophical inquiry, demonstrating that this supposed universal faculty is, in fact, a product of its time, shaped by prevailing knowledge and cultural assumptions.
In ancient Greece, the concept of koinē aisthēsis (common sense) was primarily understood as a faculty that unified the five senses, allowing for coherent perception of reality. Aristotle, in his De Anima, posited a "common sense" that acted as a central processor, integrating sensory input to form a unified experience of an object. For him, this was a biological and cognitive function, essential for recognizing differences and similarities between perceived items. However, this understanding was rooted in a philosophical framework where reason and sensory experience were intertwined, and the "common" aspect referred to a shared human capacity rather than widely held beliefs. Philosophical discourse, rather than popular opinion, defined the boundaries of this faculty.
The Enlightenment in Europe marked a significant shift. Thinkers like John Locke and Thomas Reid began to associate common sense more closely with widely accepted, practical truths that individuals possessed without formal schooling or extensive reasoning. Locke, in his Essay Concerning Human Understanding (1689), argued that some truths were obvious to "all Mankind" and did not require proof, suggesting a foundational layer of knowledge accessible to everyone. Reid, a Scottish philosopher and a prominent figure in the Scottish Enlightenment, actively championed common sense as a reliable guide against the skeptical philosophies of his day, particularly those of David Hume. Reid believed that our natural, unexamined beliefs about the world—that objects exist independently, that cause precedes effect, that we have free will—were the bedrock of common sense and should not be doubted. This period saw common sense become increasingly tied to the empirical and the practical, a bulwark against abstract intellectualism.
As scientific understanding advanced, particularly from the 17th century onwards, the boundaries of common sense were continually redefined. Galileo Galilei’s telescopic observations challenging the geocentric model of the universe, or Isaac Newton's laws of motion, were initially met with resistance precisely because they contradicted the common-sense, everyday experience of a stationary Earth and celestial spheres governed by visible, intuitive forces. The scientific revolution, in essence, involved a process of unlearning certain common-sense assumptions in favor of evidence-based reasoning, even when that reasoning led to counter-intuitive conclusions. What was "common sense" for Aristotelian physics became untenable with the advent of Newtonian mechanics. This illustrates how scientific progress can actively dismantle previously held common sense beliefs, replacing them with more complex, abstract, but ultimately more accurate understandings.
The 20th and 21st centuries have seen common sense further complicated by the rise of mass media, globalization, and the internet. Information, and misinformation, can spread with unprecedented speed, influencing what is widely accepted as true or sensible. The term "common sense" is now frequently invoked in political discourse and everyday arguments, often as a rhetorical tool to validate one's own position by framing it as universally obvious. However, the very act of disagreeing on what constitutes "common sense" in contemporary debates—whether about climate change, public health measures, or economic policy—highlights its subjective and culturally conditioned nature. Furthermore, advancements in fields like psychology and neuroscience continue to probe the cognitive underpinnings of intuitive judgment, revealing that our "common sense" can be prone to biases and heuristics, leading us astray in predictable ways. The evolution of common sense, therefore, is not just a historical narrative of ideas, but an ongoing exploration of the human mind's relationship with knowledge and reality.