Common sense
Common sense denotes the fundamental, self-evident principles of judgment and perception that rational agents universally accept as true, enabling practical navigation of the world without recourse to elaborate philosophical argument.[1] These include convictions such as the existence of an external material reality, the trustworthiness of the senses in apprehending it, and the continuity of personal identity over time, which resist skeptical undermining because their denial leads to incoherence in human belief and action.[2][1] In philosophy, common sense gained prominence as a systematic response to skepticism, particularly the empiricist doubts raised by David Hume regarding causation, induction, and the external world.[1] Thomas Reid, an 18th-century Scottish thinker, formalized this approach in works like An Inquiry into the Human Mind on the Principles of Common Sense (1764), positing that such principles are original endowments of the human constitution, not derived from reasoning but serving as its unassailable foundations.[2][1] Reid's common sense realism countered both Humean skepticism and the representationalism of earlier philosophers like John Locke and George Berkeley, advocating direct apprehension of objects rather than mediated ideas.[1] This school influenced subsequent epistemology, including G.E. Moore's 20th-century defenses against idealism and skepticism by appealing to mundane certainties, such as the existence of one's own hands.[3] Historically, the concept traces roots to Aristotle's notion of koinē aisthēsis, a integrative sensory faculty, but Reid's version emphasized epistemic priority over abstract theorizing.[4] Controversies arise from tensions with scientific paradigms that challenge intuitive assumptions—such as quantum mechanics questioning macroscopic causality—yet proponents argue common sense retains authority in domains where empirical success validates it, privileging observable regularities over ungrounded speculation.[5] In contemporary epistemology, it underpins defenses against radical revisionism, asserting that wholesale rejection of common-sense commitments undermines the very pursuit of knowledge.[6]Definition and Core Concepts
Philosophical Definition
In Aristotelian philosophy, common sense, termed koinē aisthēsis or sensus communis, constitutes a central perceptive capacity within the soul that discriminates and integrates impressions from the five special senses—sight, hearing, touch, taste, and smell—enabling the awareness of common sensibles such as unity, multiplicity, shape, size, motion, and rest.[7] This faculty does not operate as an additional sense organ but as a judging power inherent to the sensitive soul, allowing for the synthesis of sensory data into coherent perceptions beyond the grasp of any single sense.[8] The epistemic dimension of common sense emerged prominently in early modern philosophy, particularly through Thomas Reid's formulation as self-evident first principles or intuitive judgments universally assented to by rational beings without requiring demonstration.[1] Reid identified these principles as foundational to knowledge, including convictions such as the reality of external objects perceived by the senses ("Those things do really exist which we distinctly perceive by our senses") and the reliability of memory ("Those things did really happen which I distinctly remember").[1] These axioms, grounded in the structure of human faculties and ordinary language, possess immediate evidence comparable to mathematical axioms and command the consent of all ages, nations, and capacities of mind.[1] Reid's common sense philosophy serves as a direct rebuttal to skepticism, exemplified by David Hume's doubts regarding causality and the external world, by positing that denial of these principles leads to absurdities incompatible with practical human conduct.[1] Unlike speculative reasoning, which may err, common sense principles derive authority from their necessity for coherent thought and action, with philosophy tasked not to undermine but to elucidate them empirically through observation of human judgment.[1] This approach underscores common sense as the bedrock of epistemology, privileging intuitive certainties over hypothetical constructs that sever belief from perception.[1]Distinction from Specialized Knowledge
Common sense differs from specialized knowledge in its accessibility, scope, and epistemological foundations. It constitutes intuitive judgments derived from ordinary human experience, universally available without formal training, enabling practical navigation of everyday realities such as spatial orientation or social interactions.[9] In contrast, specialized knowledge requires extended education and institutional validation, focusing on abstract or technical domains like advanced scientific theories or professional expertise, which are not intuitively grasped by the general populace.[9] Philosophically, this distinction traces to ancient formulations, where Aristotle differentiated phronesis—practical wisdom akin to common sense, involving deliberative judgment in contingent matters—with episteme, systematic knowledge of unchanging principles through demonstration.[10] Phronesis operates in the realm of human action and variability, relying on habituated perception rather than universal deduction, whereas episteme underpins theoretical sciences demanding rigorous proof.[10] Later thinkers, such as Thomas Reid in the 18th century, positioned common sense as comprising self-evident first principles—such as the reliability of perception and memory—that underpin all rational inquiry, including scientific endeavors, without needing further justification.[1] Reid argued these principles are innate and non-inferential, forming the bedrock against skepticism, while specialized knowledge emerges from methodical application of observation and laws, as in Newtonian physics.[1] The interplay reveals tensions: common sense provides pragmatic reliability for routine affairs but yields to expert methods in extraordinary contexts, where empirical verification supplants intuitive assumption.[9] Reid contended that denying common sense undermines science itself, as the latter presupposes trust in sensory evidence and causal regularity—hallmarks of commonsensical belief.[1] Nonetheless, specialized knowledge often revises commonsensical intuitions, as seen in scientific advancements challenging naive perceptions, such as heliocentrism overturning geocentric assumptions prevalent in ordinary judgment.[11] This dynamic underscores common sense's foundational yet limited role, subordinate to expertise in precision-demanding fields.[12]Etymology and Evolution of the Term
The term "common sense" originates from Aristotle's concept of koinē aisthēsis (κοινὴ αἴσθησις), introduced around 350 BCE in De Anima (Book III), where it denotes a central perceptive faculty responsible for unifying and discriminating sensory data from the five external senses, such as distinguishing that a single object is both white (via sight) and sweet (via taste).[13][4] This internal power, distinct from individual senses, enables awareness of the senses' operations and judgments about perceptual qualities like shape or number.[14] In Latin philosophy, Aristotle's koinē aisthēsis was translated as sensus communis, a term employed by Roman thinkers and preserved in medieval scholasticism; for instance, Thomas Aquinas (c. 1225–1274) adopted it to describe the soul's common sensory power that integrates particular sense impressions into coherent perceptions, influencing later epistemological frameworks.[15][16] During the Renaissance and early modern period, sensus communis acquired dual connotations: retaining its perceptual role while also signifying a shared human faculty for practical judgment, as seen in Cicero's (106–43 BCE) usage for communal moral sense or public reason accessible to all.[8] By the Enlightenment, the English phrase "common sense"—a direct calque of sensus communis—evolved from a primarily sensory notion to emphasize innate, self-evident principles of rationality and everyday judgment, countering radical skepticism; Thomas Reid (1710–1796) formalized this in his 1764 Inquiry into the Human Mind, positing "principles of common sense" as original judgments indispensable for knowledge, such as the reliability of perception or causality.[1] This shift marked "common sense" as a philosophical bulwark against doubt, influencing Scottish realism and broader modern usage for practical wisdom shared by ordinary people, distinct from specialized expertise.[17]Historical Development
Ancient Greek and Roman Foundations
Aristotle (384–322 BCE) laid the foundational philosophical treatment of common sense in his De Anima, composed around 350 BCE, where he described koinē aisthēsis (common sense or common perception) as a distinct perceptual capacity beyond the five special senses of sight, hearing, smell, taste, and touch.[7] This faculty perceives "common sensibles"—qualities like motion, rest, number, magnitude, and shape that multiple senses can detect—and integrates disparate sensory inputs into unified awareness, enabling animals to recognize simultaneity in perceptions, such as seeing and hearing the same event.[18] Aristotle emphasized that common sense also facilitates incidental perception, such as inferring an object's sweetness from its color, and self-awareness of the act of perceiving itself, distinguishing it from mere mechanical sensory response.[19] In contrast to Plato's (c. 428–348 BCE) prioritization of rational dialectic and recollection over sensory flux in works like the Theaetetus, where perception alone yields opinion rather than true knowledge, Aristotle integrated common sense into an empirical framework, viewing it as essential for practical cognition and biological function across species.[20] This approach privileged observable causal interactions between perceiver and environment, grounding judgment in shared perceptual realities rather than abstract forms. Pre-Aristotelian thinkers like Empedocles had hinted at sensory coordination, but Aristotle systematized it as a unified power, countering skeptical dismissals of sense reliability in early Greek philosophy.[21] Roman adoption preserved and adapted these Greek foundations, with Cicero (106–43 BCE) employing sensus communis in De Oratore (55 BCE) to signify a cultivated shared judgment bridging individual perception and communal rhetoric, shifting emphasis toward social and ethical discernment.[22] Stoic philosophers, drawing on Aristotelian perceptual realism, developed koinai ennoiai (common conceptions)—universal innate notions of good, justice, and divinity imprinted by nature and assented to by reason—as evidentiary against radical skepticism, influencing Roman thinkers like Seneca (c. 4 BCE–65 CE) in ethical applications.[23] This evolution from perceptual integration to rational universals underscored common sense's role in moral and epistemic stability amid Roman practical philosophy.[17]Medieval and Early Modern Interpretations
In medieval philosophy, the concept of sensus communis, derived from Aristotle's De Anima (c. 350 BCE), was elaborated as a central internal sense faculty that integrates and discriminates impressions from the five external senses, enabling unified perception beyond isolated sensory inputs.[24] Islamic philosopher Avicenna (Ibn Sina, 980–1037 CE) advanced this in his Kitab al-Shifa (c. 1020s), positing sensus communis as the first internal sense, located in the anterior part of the brain's first ventricle, where it receives and stores sensory forms for further processing by faculties like imagination and estimation, thus forming the basis for coherent animal and human cognition.[25] [26] This framework influenced Latin Scholasticism after translations in the 12th century. Thomas Aquinas (1225–1274 CE), in his Summa Theologica (1265–1274) and commentaries on Aristotle, adopted and refined the doctrine, identifying sensus communis as one of four internal senses (alongside imagination, the cogitative/estimative power, and memory), responsible for judging sensory data's validity, distinguishing proper sensibles (e.g., color for sight), and synthesizing perceptions into a unified act essential for intellectual abstraction.[27] [28] Aquinas emphasized its non-intellectual nature, rooted in the sensitive appetite, yet preparatory for reason, aligning with empirical observation of animal perception while subordinating it to divine intellect in human knowing.[29] In early modern philosophy, sensus communis shifted from primarily perceptual integration toward social, rhetorical, and moral dimensions, reflecting humanist and Enlightenment precursors. Giambattista Vico (1668–1744), in De Antiquissima Italorum Sapientia (1710) and Principi di Scienza Nuova (1725/1744), reconceived it as the collective, historically emergent sense of a people's customs, language, and truths, enabling verifiability through human-made (verum factum) principles rather than abstract deduction, thus grounding jurisprudence and history in communal judgment over Cartesian individualism.[30] [31] Anthony Ashley-Cooper, 3rd Earl of Shaftesbury (1671–1713), in his essay "Sensus Communis: An Essay on the Freedom of Wit and Humour" (1709), portrayed it as an innate moral-aesthetic faculty attuned to harmony and the common good, cultivated through sociable wit and raillery to discern virtue amid self-interest, influencing later sentimentalist ethics by prioritizing natural affections over rational calculation alone.[32] [17] These interpretations bridged medieval sensory psychology with emerging views of shared practical reason, anticipating but distinct from 18th-century common sense realism's epistemological focus.[33]Enlightenment Era Formulations
During the early Enlightenment, Anthony Ashley-Cooper, 3rd Earl of Shaftesbury, articulated a key formulation of common sense in his 1709 essay Sensus Communis: An Essay on the Freedom of Wit and Humour, reviving the ancient Stoic concept of sensus communis as an innate capacity for discerning the common good and public welfare.[34] Shaftesbury described this common sense as a natural, universal faculty that enables individuals to judge social and moral matters intuitively, without reliance on abstract reasoning, emphasizing its role in fostering harmony and virtue in civil society.[32] He linked it to a broader moral sense theory, positing that humans possess an implanted inclination toward benevolence and sympathy, allowing immediate apprehension of moral beauty or deformity in actions and characters.[35] Shaftesbury's view positioned common sense as a counter to excessive skepticism and individualism, arguing it operates as a "first principle" in human constitution, universally accessible yet refined through social intercourse and reflection.[35] This innate moral intuition contrasted sharply with John Locke's empiricist rejection of innate ideas, where common sense emerges instead from sensory experience and habitual judgment accumulated over time to fulfill epistemic duties.[36] Shaftesbury's emphasis on natural, pre-reflective discernment of the "common interest of mankind" influenced the trajectory of British Enlightenment thought, promoting a secular ethics grounded in shared human sentiments rather than divine imposition or pure rationalism.[33] David Hume, building on moral sense traditions, incorporated elements of common sense into his ethics by deriving moral distinctions from sentiments of pleasure and pain in approbation, rather than reason alone, though he treated epistemological common sense pragmatically as custom overriding skeptical doubts in everyday practice.[37] Hume's approach thus preserved common sense as a practical foundation for belief and action, acknowledging its reliability in navigating causal inferences and external reality despite philosophical challenges to their justification.[38] These formulations highlighted common sense's role in balancing Enlightenment rational inquiry with intuitive, socially embedded judgment, prefiguring later realist responses to empiricist skepticism.[34]Major Philosophical Traditions
Aristotelian and Thomistic Common Sense
In Aristotle's De Anima, composed around 350 BCE, the concept of koinē aisthēsis (common sense) refers to a central perceptual faculty of the soul that perceives "common sensibles" such as motion, rest, number, magnitude, and unity, which are detectable by more than one external sense but not proper to any single one.[7] This faculty integrates simultaneous inputs from the five external senses—sight, hearing, smell, taste, and touch—enabling awareness of a unified object, for instance, recognizing that a seen white shape coincides with a heard sound or tasted sweetness.[39] Aristotle posits koinē aisthēsis as a single power rather than multiple faculties, arguing it discriminates differences between sensible qualities across senses and accounts for phenomena like noticing pleasure or pain in perception, thereby providing a causal explanation for the unity of sensory experience grounded in the soul's form actualizing the body's potential.[40] Thomas Aquinas, in his Summa Theologica (1265–1274), adopts and refines Aristotle's framework within a Christian hylomorphic anthropology, designating sensus communis as the primary internal sense that receives intentional species (sensible forms) from the external senses without altering them.[41] Unlike the external senses, which apprehend proper sensibles (e.g., color by sight alone), sensus communis judges the concordance of these inputs—verifying, for example, that the visible object matches the audible one—and perceives the composite sensible whole, such as an apple's integrated color, shape, and odor.[42] Aquinas distinguishes it from other internal senses: imagination stores and composes these unified images, the cogitative power (particular reason in humans) estimates particulars for utility or harm, and memory retains them with temporal sequencing; collectively, they prepare phantasms for intellectual abstraction, ensuring sensory data's reliability as the foundation for certain knowledge.[43] This Aristotelian-Thomistic common sense operates as a pre-noetic integrator, rooted in empirical observation of perceptual unity rather than skepticism, countering views that fragment experience into isolated qualia; its causal realism posits the soul's sensitive powers as formally identical across organs yet numerically distinct in acts, avoiding dualistic separation while explaining illusions as misjudgments of accidental sensibles.[44] In epistemology, it underpins the ascent from particulars to universals, privileging direct sensory causation over innate ideas, with Aquinas emphasizing its passivity in reception but activity in judgment to affirm truth against deceptive appearances.[28] Scholarly analyses confirm this faculty's role in resolving Aristotelian puzzles, such as incidental perception of common objects, without invoking modern representationalism.[16]Cartesian Skepticism and Responses
In his Meditations on First Philosophy (1641), René Descartes initiated a program of methodological skepticism by systematically doubting all propositions susceptible to any degree of uncertainty, including those rooted in sensory experience and everyday intuition.[45] This approach directly confronted common sense assumptions about the reliability of perception, as Descartes highlighted cases of sensory deception—such as optical illusions, hallucinations, and the indistinguishability of waking life from dreams—to argue that no empirical belief could claim indubitability.[45] He further escalated doubt through hypothetical scenarios, like an omnipotent deceiver systematically falsifying all cognitions, which extended skepticism even to mathematical truths previously deemed self-evident.[45] By demolishing these foundations, Descartes aimed to expose the fragility of common sense as a basis for knowledge, privileging hyperbolic doubt over unexamined trust in faculties prone to error. Descartes' own resolution to this skepticism preserved a role for rational reconstruction rather than wholesale endorsement of common sense. Through relentless doubt, he identified the cogito ergo sum—"I think, therefore I am"—as an unshakeable truth, establishing the existence of the self as a thinking substance immune to deception.[45] From this Archimedean point, he invoked innate ideas and proofs for God's existence and non-deceptiveness, arguing that clear and distinct perceptions (including those of the external world) are trustworthy when guaranteed by a benevolent deity.[45] This foundationalist strategy rehabilitated sensory beliefs for practical purposes but subordinated them to intellectual criteria, effectively critiquing common sense as insufficiently rigorous without rational validation.[45] Subsequent philosophers, particularly in the Scottish Enlightenment, mounted direct challenges to Cartesian skepticism by defending common sense as an irreducible bulwark against doubt. Thomas Reid, in An Inquiry into the Human Mind on the Principles of Common Sense (1764), rejected the Cartesian "way of ideas"—the theory that perceptions represent rather than directly apprehend external objects—as the root cause of skepticism, contending it artificially severs mind from reality.[1] Reid posited that common sense operates through original faculties yielding self-evident first principles, such as the belief in an external world and the trustworthiness of memory, which cannot coherently be doubted without undermining all judgment.[1] For Reid, the skeptic's arguments, including Descartes' demon hypothesis, fail not by refutation but by their impracticality: skeptics inevitably act upon common sense convictions in daily life, revealing doubt as a philosophical affectation rather than a viable epistemology.[1] This reliabilist response emphasized the causal reliability of human cognitive constitution, forged by design or nature, over abstract foundationalism.[1]