ekstensionalisuuskäsitteet

Extensionality concepts, or "ekstensionalisuuskäsitteet" in Finnish, refer to philosophical and logical principles that focus on the extension of a concept or term. The extension of a term is the set of all things to which that term applies. For example, the extension of the term "dog" is the set of all actual dogs. Extensionality principles assert that two concepts or terms are identical if and only if they have the same extension.

In logic, extensionality is a fundamental principle. For instance, in set theory, two sets are considered equal if they contain precisely the same elements, regardless of how those elements are described or ordered. This is the principle of extensionality for sets. Similarly, in propositional logic, two statements are logically equivalent if they have the same truth value in all possible circumstances. This relates to the idea that the meaning or value of a statement is determined by its truth conditions, which are tied to its extension (the conditions under which it is true).

However, not all areas of thought strictly adhere to extensionality. In areas like psychology or semantics, intensionality plays a significant role. Intension refers to the meaning or concept associated with a term, rather than the set of things it denotes. For example, the terms "morning star" and "evening star" have the same extension (the planet Venus), but they have different intensions (different concepts or ways of referring to Venus). Debates about the role and scope of extensionality versus intensionality are central to many philosophical discussions concerning language, meaning, and knowledge.