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Common sense

Basic level of knowledge and judgement shared by nearly all people

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"Common sense" has at least two older and more specialized meanings which have influenced the modern meanings, and are still discussed in philosophy—one is specific to the common ability to perceive using the senses, and the other relates to a shared sense of community or humanity. The original historical meaning, often referred to using the medieval Latin term Sensus communis, is the "sense" within the animal soul (ψῡχή, psūkhḗ) originally proposed by Aristotle, which perceives real things based on different sensory perceptions from distinct senses (sights, sounds, smells and so on). 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." Interest in this concept was partly in reaction to Descartes's critical remarks about the French term bon sens, and it was connected to the dispute between "rationalism" and "empiricism" and the arguments for different types of scientific method. In the opening line of one of his most famous books, Discourse on Method, Descartes stated that everyone has a similar and sufficient amount of common or good sense (bon sens), but it is rarely used well. Therefore, a skeptical logical method 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.

Classical philosophical predecessors

The origin of the term "common sense" (Latin: Sensus communis, Ancient Greek: koinḕ aísthēsis) is in the works of Aristotle, although the way he used the term had a very different meaning to the one most common in modern English. Nevertheless, his original "common sense" represents a very long-lasting and successful proposal, which can still be referred to in English using the English, Greek or Latin terms. Heller-Roazen (2008) writes that "In different ways the philosophers of medieval Latin and Arabic tradition, from Al-Farabi to Avicenna, Averroës, Albert, and Thomas, found in the De Anima and the Parva Naturalia the scattered elements of a coherent doctrine of the "central" faculty of the sensuous soul." It was "one of the most successful and resilient of Aristotelian notions".

The Latin term Sensus communis developed yet another meaning during the time of the Roman Empire in the earlier Latin of the Roman Empire, different from both Aristotle's concept and the most typical meaning in modern English, and this also continues to be discussed in philosophical literature. These especially Roman meanings were apparently influenced by several Stoic Greek terms with the word koinḗ (κοινή, 'common, shared'); not only koinḕ aísthēsis, but also such terms as koinós noûs (κοινός νοῦς, 'common mind/thought/reason'), koinḗ énnoia (κοινή ἔννοιᾰ), and koinonoēmosúnē, all of which involve noûs—something, at least in Aristotle, that would not be present in "lower" animals.

  • Koinḗ énnoia is a term from Stoic philosophy, a Greek philosophy, influenced by Aristotle, and influential in Rome. This refers to shared notions, or common conceptions, that are either in-born or imprinted by the senses onto the soul. Unfortunately few true Stoic texts survive, and our understanding of their technical terminology is limited.
  • Koinós noûs is a term found in Epictetus (III.vi.8), a Stoic philosopher. C.S. Lewis (1967, p. 146) believed this to be close to a modern English meaning of "common sense", "the elementary mental outfit of the normal man", something like intelligence. He noted that sensus could be a translation of noûs, (for example in the Vulgate Bible), but he only found one clear case of a Latin text showing this apparent meaning, a text by Phaedrus the fable writer.
  • Koinonoēmosúnē is found only in the work of the emperor Marcus Aurelius (Meditations I.16), also known as a Stoic. He uses the word on its own in a list of things he learned from his adopted father. Anthony Ashley Cooper, 3rd Earl of Shaftesbury felt it represented the Stoic Greek original, which gave the special Roman meaning of sensus communis, especially when used to refer to someone's public spirit. He explained the change of meaning as being due to the specific way that Stoics understood perception and intellect, saying that one should "consider withal how small the distinction was in that Philosophy, between the ὑπόληψις [conjecture], and the vulgar αἴσθησις [perception]; how generally Passion was by those Philosophers brought under the Head of Opinion".

Roman communis sensus was probably influenced instead by a different term of Aristotle used in his study of rhetoric, a subject that Aristotle was the first to systematize. In rhetoric, a prudent speaker must take account of opinions (δόξαι, dóxai) that are widely held. Aristotle referred to such commonly held beliefs not as koinaí dóxai (κοιναί δόξαι, lit. ''common opinions''), which is a term he used for self-evident logical axioms, but with other terms such as éndóxa (ἔνδόξα).

In his Rhetoric for example Aristotle mentions "koinōn [...] tàs písteis" or "common beliefs", saying that "our proofs and arguments must rest on generally accepted principles, [...] when speaking of converse with the multitude". In a similar passage in his own work on rhetoric, De Oratore, Cicero wrote that "in oratory the very cardinal sin is to depart from the language of everyday life and the usage approved by the sense of the community." The sense of the community is in this case a translation of "communis sensus" in the Latin of Cicero.

Whether the Latin writers such as Cicero deliberately used this Aristotelian rhetoric term in a new more peculiarly Roman way, probably also influenced by Greek Stoicism, therefore remains a subject of discussion. Schaeffer (1990, p. 112) has proposed for example that the Roman Republic maintained a very "oral" culture whereas in Aristotle's time rhetoric had come under heavy criticism from philosophers such as Socrates. Peters Agnew (2008) argues, in agreement with Shaftesbury, that the concept developed from the Stoic concept of ethical virtue, influenced by Aristotle, but emphasizing the role of both individual perception and shared communal understanding. A complex of ideas attached itself to the term, to be almost forgotten in the Middle Ages, and eventually returning into ethical discussion in 18th-century Europe, after Descartes.

As with other meanings of common sense, for the Romans of the classical era "it designates a sensibility shared by all, from which one may deduce a number of fundamental judgments, that need not, or cannot, be questioned by rational reflection". But even though Cicero did at least once use the term in a manuscript on Plato's Timaeus (concerning a primordial "sense, one and common for all [...] connected with nature"), he and other Roman authors did not normally use it as a technical term limited to discussion about sense perception, as Aristotle apparently had in De Anima, and as the Scholastics later would in the Middle Ages. Instead of referring to all animal judgment, it was used to describe pre-rational, widely shared human beliefs, and therefore it was a near equivalent to the concept of humanitas. This was a term that could be used by Romans to imply not only human nature, but also humane conduct, good breeding, refined manners, and so on. Apart from Cicero, Quintilian, Lucretius, Seneca, Horace and some of the most influential Roman authors influenced by Aristotle's rhetoric and philosophy used the Latin term "sensus communis" in a range of such ways. As C. S. Lewis wrote:

Quintilian says it is better to send a boy to school than to have a private tutor for him at home; for if he is kept away from the herd (congressus) how will he ever learn that sensus which we call communis? (I, ii, 20). On the lowest level it means tact. In Horace the man who talks to you when you obviously don't want to talk lacks communis sensus.

Compared to Aristotle and his strictest medieval followers, these Roman authors were not so strict about the boundary between animal-like common sense and specially human reasoning. As discussed above, Aristotle had attempted to make a clear distinction between, on the one hand, imagination and the sense perception which both use the sensible koiná, and which animals also have; and, on the other hand, noûs (intellect) and reason, which perceives another type of koiná, the intelligible forms, which (according to Aristotle) only humans have. In other words, these Romans allowed that people could have animal-like shared understandings of reality, not just in terms of memories of sense perceptions, but in terms of the way they would tend to explain things, and in the language they use.

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