Common sense is sound practical judgment concerning everyday matters, or a basic ability to perceive, understand, and judge that is shared by (“common to”) nearly all people. The first type of common sense, good sense, can be described as “the knack for seeing things as they are, and doing things as they ought to be done.” The second type is sometimes described as folk wisdom, “signifying unreflective knowledge not reliant on specialized training or deliberative thought.” The two types are intertwined, as the person who has common sense is in touch with common-sense ideas, which emerge from the lived experiences of those commonsensical enough to perceive them.In a psychology context, Smedslund defines common sense as “the system of implications shared by the competent users of a language” and notes, “A proposition in a given context belongs to common sense if and only if all competent users of the language involved agree that the proposition in the given context is true and that its negation is false.”The everyday understanding of common sense derives from historical philosophical discussion involving several European languages. Related terms in other languages include Latin sensus communis, Greek αἴσθησις κοινὴ (aísthēsis koinḕ), and French bon sens, but these are not straightforward translations in all contexts. Similarly in English, there are different shades of meaning, implying more or less education and wisdom: “good sense” is sometimes seen as equivalent to “common sense”, and sometimes not.
“Common sense” also has at least two specifically philosophical meanings. One is a capability of the animal soul (ψῡχή, psūkhḗ) proposed by Aristotle, which enables different individual senses to collectively perceive the characteristics of physical things such as movement and size, which all physical things have in different combinations, allowing people and other animals to distinguish and identify physical things. This common sense is distinct from basic sensory perception and from human rational thinking, but cooperates with both.
The second special use of the term is Roman-influenced and is used for the natural human sensitivity for other humans and the community. Just like the everyday meaning, both of these refer to a type of basic awareness and ability to judge that most people are expected to share naturally, even if they cannot explain why.
All these meanings of “common sense”, including the everyday ones, are interconnected in a complex history and have evolved during important political and philosophical debates in modern Western civilisation, notably concerning science, politics and economics. The interplay between the meanings has come to be particularly notable in English, as opposed to other western European languages, and the English term has become international.Since the Age of Enlightenment the term “common sense” has frequently been used for rhetorical effect, sometimes pejorative, and sometimes appealed to positively, as an authority. It can be negatively equated to vulgar prejudice and superstition, or on the contrary it is often positively contrasted to them as a standard for good taste and as the source of the most basic axioms needed for science and logic. It was at the beginning of the eighteenth century that this old philosophical term first acquired its modern English meaning: “Those plain, self-evident truths or conventional wisdom that one needed no sophistication to grasp and no proof to accept precisely because they accorded so well with the basic (common sense) intellectual capacities and experiences of the whole social body”
This began with Descartes’ criticism of it, and what came to be known as the dispute between “rationalism” and “empiricism”. In the opening line of one of his most famous books, Discourse on Method, Descartes established the most common modern meaning, and its controversies, when he stated that everyone has a similar and sufficient amount of common sense (bon sens), but it is rarely used well. Therefore, a skeptical logical method described by Descartes needs to be followed and common sense should not be overly relied upon. In the ensuing 18th century Enlightenment, common sense came to be seen more positively as the basis for modern thinking. It was contrasted to metaphysics, which was, like Cartesianism, associated with the Ancien Régime. Thomas Paine’s polemical pamphlet Common Sense (1776) has been described as the most influential political pamphlet of the 18th century, affecting both the American and French revolutions. Today, the concept of common sense, and how it should best be used, remains linked to many of the most perennial topics in epistemology and ethics, with special focus often directed at the philosophy of the modern social sciences.