Editing Intension (section)

=== Extensional statement form ===
{{Main|Extensional context|Extensionality|Extension (semantics)}}

An ''extensional'' statement is a non-intensional statement. Substitution of co-extensive expressions into it always preserves logical value. A language is intensional if it contains intensional statements, and extensional otherwise. All natural languages are intensional.<ref>{{Cite journal|last=Carnap|first=Rudolf|date=April 1955|title=Meaning and synonymy in natural languages|url=http://link.springer.com/10.1007/BF02330951|journal=Philosophical Studies|language=en|volume=6|issue=3|pages=33–47|doi=10.1007/BF02330951|s2cid=170508331 |issn=0031-8116|url-access=subscription}}</ref> The only extensional languages are artificially constructed languages used in [[mathematical logic]] or for other special purposes and small fragments of natural languages.

==== Examples ====
#Mark Twain wrote ''Huckleberry Finn''.
#Aristotle enjoyed stargazing.

Note that if "[[Samuel Clemens]]" is put into (1) in place of "Mark Twain", the result is as true as the original statement. It should be clear that no matter what is put for "Mark Twain", so long as it is a singular term picking out the same man, the statement remains true. Likewise, we can put in place of the [[Predicate (mathematical logic)|predicate]] any other predicate belonging to Mark Twain and only to Mark Twain, without changing the logical value. 

For (2), the term "stargazing" can now be substituted with "looking at luminous spheroids of plasma held together by self-gravity", since Aristotle personally being aware of the two terms being co-extensive is no longer relevant to the logical value of the sentence.