In philosophy and logic (especially metaphysics), a property is a characteristic of an object; for example, a red object is said to have the property of redness. The property may be considered a form of object in its own right, able to possess other properties. A property, however, differs from individual objects in that it may be instantiated, and often in more than one object. It differs from the logical and mathematical concept of class by not having any concept of extensionality, and from the philosophical concept of class in that a property is considered to be distinct from the objects which possess it. Understanding how different individual entities (or particulars) can in some sense have some of the same properties is the basis of the problem of universals.
Terms and usage A property is any member of a class of entities that are capable of being attributed to objects. Terms similar to property include predicable, attribute, quality, feature, characteristic, type, exemplifiable, predicate, and intensional entity. Generally speaking, an object is said to exemplify, instantiate, bear, have or possess a property if the property can be truly predicated of the object. The collection of objects that possess a property is called the extension of the property. Properties are said to characterize or inhere in objects that possess them. Followers of Alexius Meinong assert the existence of two kinds of predication: existent objects exemplify properties, while nonexistent objects are said to exemplify, satisfy, immanently contain or be consubstantiated by properties that are actually possessed and are said to encode, be determined by, be consociated with or be constituted by properties that are merely ascribed to objects. For example, since Pegasus is merely mythical, Pegasus encodes the property of being a horse, but Pegasus exemplifies the property of being a character of Greek mythology as well. Edward Jonathan Lowe even treated instantiation, characterization and exemplification as three separate kinds of predication. Broadly construed, examples of properties include redness, the property of being two, the property of being nonexistent, the property of being identical to Socrates, the property of being a desk, the property of being a property, the property of being both round and square, and the property of being heterological. Some philosophers refuse to treat existence as a property, and Peter van Inwagen suggested that one should deny the existence of certain "properties" so as to avoid paradoxes such as Russell's paradox and Grelling–Nelson paradox, though such moves remain controversial.
Metaphysical debates In modern analytic philosophy there are several debates about the fundamental nature of properties. These center around questions such as: Are properties universals or particulars? Are properties real? Are they categorical or dispositional? Are properties physical or mental?
Universals vs. particulars At least since Plato, properties are viewed by numerous philosophers as universals, which are typically capable of being instantiated by different objects. Philosophers opposing this view regard properties as particulars, namely tropes.
Realism vs. anti-realism A realist about properties asserts that properties have genuine, mind-independent existence. One way to spell this out is in terms of exact, repeatable, instantiations known as universals. The other realist position asserts that properties are particulars (tropes), which are unique instantiations in individual objects that merely resemble one another to various degrees. Transcendent realism, proposed by Plato and favored by Bertrand Russell, asserts that properties exist even if uninstantiated. Immanent realism, defended by Aristotle and David Malet Armstrong, contends that properties exist only if instantiated. The anti-realist position, often referred to as nominalism claims that properties are names we attach to particulars. The properties themselves have no existence.
Categoricalism vs. dispositionalism Properties are often classified as either categorical and dispositional. Categorical properties concern what something is like, e.g. what qualities it has. Dispositional properties, on the other hand, involve what powers something has, what it is able to do, even if it is not actually doing it. For example, the shape of a sugar cube is a categorical property while its tendency to dissolve in water is a dispositional property. For many properties there is a lack of consensus as to how they should be classified, for example, whether colors are categorical or dispositional properties. According to categoricalism, dispositions reduce to causal bases. On this view, the fragility of a wine glass, a dispositional property, is not a fundamental feature of the glass since it can be explained in terms of the categorical property of the glass's micro-structural composition. Dispositionalism, on the other hand, asserts that a property is nothing more than a set of causal powers. Fragility, according to this view, identifies a real property of the glass (e.g. to shatter when dropped on a sufficiently hard surface). Several intermediary positions exist. The Identity view states that properties are both categorical (qualitative) and dispositional; these are just two ways of viewing the same property. One hybrid view claims that some properties are categorical and some are dispositional. A second hybrid view claims that properties have both a categorical (qualitative) and dispositional part, but that these are distinct ontological parts.
Physicalism, idealism, and property dualism
Property dualism describes a category of positions in the philosophy of mind which hold that, although the world is constituted of just one kind of substance—the physical kind—there exist two distinct kinds of properties: physical properties and mental properties. In other words, it is the view that non-physical, mental properties (such as beliefs, desires and emotions) inhere in some physical substances (namely brains). This stands in contrast to physicalism and idealism. Physicalism claims that all properties, include mental properties, ultimately reduce to, or supervene on, physical properties. Metaphysical idealism, by contrast, claims that "something mental (the mind, spirit, reason, will) is the ultimate foundation of all reality, or even exhaustive of reality."
Types
Intrinsic and extrinsic
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