Common sense (from Latin sensus communis) is "knowledge, judgement, and taste which is more or less universal and which is held more or less without reflection or argument". As such, it is often considered to represent the basic level of sound practical judgement or knowledge of basic facts that any adult human being ought to possess. It is "common" in the sense of being shared by nearly all people. Relevant terms from other languages used in such discussions include the aforementioned Latin, itself translating Ancient Greek κοινὴ αἴσθησις (koinḕ aísthēsis), and French bon sens. However, these are not straightforward translations in all contexts, and in English different shades of meaning have developed. In philosophical and scientific contexts, since the Age of Enlightenment the term "common sense" has been used for rhetorical effect both approvingly and disapprovingly. On the one hand it has been a standard for good taste, good sense, and source of scientific and logical axioms. On the other hand it has been equated to conventional wisdom, vulgar prejudice, and superstition. "Common sense" has at least two older and more specialized meanings which have influenced the modern meanings, and are still important in philosophy. The original historical meaning is the capability of the animal soul (ψῡχή, psūkhḗ), proposed by Aristotle to explain how the different senses join and enable discrimination of particular objects by people and other animals. This common sense is distinct from the several sensory perceptions and from human rational thought, but it cooperates with both. The second philosophical 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 the philosophical meanings 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 in turn become international.
It was at the beginning of the 18th 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's 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 era, common sense came to be seen more positively as the basis for empiricist 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.
