Saturday, March 31, 2018

Common Sense and Aristotle

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 κοινὴ αἴσθησις (koinē aísthēsis), 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 (Greek psukhē) 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 inter-connected 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 regime. 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.

Aristotle and Common Sense

The origin of the term is in the works of Aristotle. The best-known case is De Anima Book III, chapter 2, especially at line 425a27. The passage is about how the animal mind converts raw sense perceptions from the five specialized sense perceptions, into perceptions of real things moving and changing, which can be thought about. According to Aristotle's understanding of perception, each of the five senses perceives one type of "perceptible" or "sensible" which is specific (Greek: idia) to it. For example, sight can see colour. But Aristotle was explaining how the animal mind, not just the human mind, links and categorizes different tastes, colours, feelings, smells and sounds in order to perceive real things in terms of the "common sensibles" (or "common perceptibles"). In this discussion "common" (koinos) is a term opposed to specific or particular (idia). The Greek for these common sensibles is ta koina, which means shared or common things, and examples include the oneness of each thing, with its specific shape and size and so on, and the change or movement of each thing. Distinct combinations of these properties are common to all perceived things.

In this passage, Aristotle explained that concerning these koina (such as movement) we already have a sense, a "common sense" or sense of the common things (Greek: koinē aisthēsis), which does not work by accident (Greek: kata sumbebēkos). And there is no specific (idia) sense perception for movement and other koina, because then we would not perceive the koina at all, except by accident. As examples of perceiving by accident Aristotle mentions using the specific sense perception vision on its own to see that something is sweet, or to recognize a friend by their distinctive color. Lee (2011, p. 31) explains that "when I see Socrates, it is not insofar as he is Socrates that he is visible to my eye, but rather because he is coloured". So the normal five individual senses do sense the common perceptibles according to Aristotle (and Plato), but it is not something they necessarily interpret correctly on their own. Aristotle proposes that the reason for having several senses is in fact that it increases the chances that we can distinguish and recognize things correctly, and not just occasionally or by accident. Each sense is used to identify distinctions, such as sight identifying the difference between black and white, but, says Aristotle, all animals with perception must have "some one thing" that can distinguish black from sweet. The common sense is where this comparison happens, and this must occur by comparing impressions (or symbols or markers; Greek: sēmeion) of what the specialist senses have perceived. The common sense is therefore also where a type of consciousness originates, "for it makes us aware of having sensations at all". And it receives physical picture imprints from the imaginative faculty, which are then memories that can be recollected.

The discussion was apparently intended to improve upon the account of Aristotle's friend and teacher Plato in his Socratic dialogue, the Theaetetus. But Plato's dialogue presented an argument that recognizing koina is an active thinking process in the rational part of the human soul, making the senses instruments of the thinking part of man. Plato's Socrates says this kind of thinking is not a kind of sense at all. Aristotle, trying to give a more general account of the souls of all animals, not just humans, moved the act of perception out of the rational thinking soul into this sensus communis, which is something like a sense, and something like thinking, but not rational.

The passage is difficult to interpret and there is little consensus about many of the details. Gregorić (2007, pp. 204–205) has argued that this may be because Aristotle did not use the term as a standardized technical term at all. For example, in some passages in his works, Aristotle seems to use the term to refer to the individual sense perceptions simply being common to all people, or common to various types of animals. There is also difficulty with trying to determine whether the common sense is truly separable from the individual sense perceptions and from imagination, in anything other than a conceptual way as a capability. Aristotle never fully spells out the relationship between the common sense and the imaginative faculty ("phantasia"), although the two clearly work together in animals, and not only humans, for example in order to enable a perception of time. They may even be the same. Despite hints by Aristotle himself that they were united, early commentators such as Alexander of Aphrodisias and Al-Farabi felt they were distinct, but later, Avicenna emphasized the link, influencing future authors including Christian philosophers. Gregorić (2007, p. 205) argues that Aristotle used the term "common sense" both to discuss the individual senses when these act as a unity, which Gregorić calls "the perceptual capacity of the soul", or the higher level "sensory capacity of the soul" that represents the senses and the imagination working as a unity. According to Gregorić, there appears to have been a standardization of the term koinē aisthēsis as a term for the perceptual capacity (not the higher level sensory capacity), which occurred by the time of Alexander of Aphrodisias at the latest.

Compared to Plato, Aristotle's understanding of the soul (Greek psyche) has an extra level of complexity in the form of the nous or "intellect"—which is something only humans have and enables humans to perceive things differently from other animals. It works with images coming from the common sense and imagination, using reasoning (Greek logos) as well as the active intellect. The nous identifies the true forms of things, while the common sense identifies shared aspects of things. Though scholars have varying interpretations of the details, Aristotle's "common sense" was in any case not rational, in the sense that it implied no ability to explain the perception. Reason or rationality (logos) exists only in man according to Aristotle, and yet some animals can perceive "common perceptibles" such as change and shape, and some even have imagination according to Aristotle. Animals with imagination come closest to having something like reasoning and nous. Plato, on the other hand was apparently willing to allow that animals could have some level of thought, meaning that he did not have to explain their sometimes complex behavior with a strict division between high-level perception processing and the human-like thinking such as being able to form opinions. Gregorić additionally argues that Aristotle can be interpreted as using the verbs, phronein and noein, to distinguish two types of thinking or awareness, one being found in animals, and the other unique to humans and involving reason. Therefore, in Aristotle (and the medieval Aristotelians) the universals used to identify and categorize things are divided into two. In medieval terminology these are the species sensibilis used for perception and imagination in animals, and the species intelligibilis or apprehendable forms used in the human intellect or nous.

Aristotle also occasionally called the koinē aisthēsis (or one version of it), the prōton aisthētikon, the first of the senses. (According to Gregorić this is specifically in contexts where it refers to the higher order common sense that includes imagination.) Later philosophers developing this line of thought, such as Themistius, Galen, and Al-Farabi, called it the ruler of the senses or ruling sense, apparently a metaphor developed from a section of Plato's Timaeus (70b). Augustine and some of the Arab writers, also called it the "inner sense". The concept of the inner senses, plural, was further developed in the Middle Ages. Under the influence of the great Persian philosophers Al-Farabi and Avicenna, several inner senses came to be listed. "Thomas Aquinas and John of Jandun recognized four internal senses: the common sense, imagination, vis cogitativa, and memory. Avicenna, followed by Robert Grosseteste, Albert the Great, and Roger Bacon, argued for five internal senses: the common sense, imagination, fantasy, vis aestimativa, and memory." By the time of Descartes and Hobbes, in the 1600s, the inner senses had been standardized to five wits, which complemented the more well-known five "external" senses. Under this medieval scheme the common sense was understood to be seated not in the heart, as Aristotle had thought, but in the anterior Galenic ventricle of the brain. The great anatomist Andreas Vesalius however found no connections between the anterior ventricle and the sensory nerves, leading to speculation about other parts of the brain into the 1600s.

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.”

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