A class is a collection whose members either fall under a predicate or are classified by a rule. Hence, while a set can be
extensionally defined only by its elements, a class has also an intensional dimension that unites its members. When the term 'class' is applied so that it includes those sets whose elements are intended to be collected without a common predicate or rule, the distinction can be indicated by calling such sets "improper class."
Philosopher
Philosophy ('love of wisdom' in Ancient Greek) is a systematic study of general and fundamental questions concerning topics like existence, reason, knowledge, Value (ethics and social sciences), value, mind, and language. It is a rational an ...
s sometimes distinguish classes from
types
Type may refer to:
Science and technology Computing
* Typing, producing text via a keyboard, typewriter, etc.
* Data type, collection of values used for computations.
* File type
* TYPE (DOS command), a command to display contents of a file.
* Ty ...
and
kinds. The ''class'' of human beings is discussed, as well as the ''type'' (or ''natural kind''), human being, or humanity. While both are typically treated as
abstract object
In philosophy and the arts, a fundamental distinction exists between abstract and concrete entities. While there is no universally accepted definition, common examples illustrate the difference: numbers, sets, and ideas are typically classif ...
s and not different
categories of being, types not classes are usually treated as
universals. Whether natural kinds ought to be considered universals is vexed; see
natural kind.
Types and kinds are discussed differently.
Socrates
Socrates (; ; – 399 BC) was a Ancient Greek philosophy, Greek philosopher from Classical Athens, Athens who is credited as the founder of Western philosophy and as among the first moral philosophers of the Ethics, ethical tradition ...
is considered a
''token'' of a type (or an
''instance'' of the natural kind, human being) but a ''member'' of the class of human beings. He is a token (instance) not member of the type (kind), human beings. He is a member not type (or kind) of a class. The terminology is that types (or kinds) have tokens (or instances) while classes have members.
A class is conceptualized similarly to a set defined by its members.
The class is extensional. A set defined intensionally is a set of things that meet some requirement to be a member. Such a set creates a type. It also creates a class from the extension of the intensional set. A type always has a corresponding (potentially empty) class, but a class does not necessarily have a corresponding type.
References
External links
"Class" as analytical term in philosophy Philosophypages.com
*
ttp://plato.stanford.edu/entries/logical-atomism/ "Class" as an aspect of logic, and particularly Bertrand Russell"s Principia Mathematica"From Aristotle to EA: a type theory for EA" quoted 26/10/2014.
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Concepts in logic