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intensions

Intensions refer to the sense or concept associated with a term, as opposed to its extension, which is the actual set of objects the term applies to in a given world. An intension can be thought of as the conditions, properties, or mental content that determine whether something falls under a term. In this view, the extension of a term can vary across possible worlds, while its intension remains the underlying concept.

In formal semantics, especially in possible-worlds semantics, the intension of a predicate is modeled as a function

Intensional contexts include belief, desire, necessity, and possibility. In such contexts, substituting co-extensional terms can change

Historically, the distinction between sense (often linked to Frege’s Sinn) and reference underlies the development of

A typical example contrasts a term’s intension with its extension: the intension of “bachelor” includes being

from
possible
worlds
to
extensions.
For
each
world,
the
function
yields
the
set
of
individuals
that
satisfy
the
predicate
in
that
world.
This
makes
intensions
central
to
the
study
of
modal
and
non-extensional
contexts,
where
truth
conditions
depend
on
more
than
the
actual
objects
in
the
world.
truth
conditions,
because
the
terms
may
share
the
same
extension
in
the
actual
world
but
differ
in
intension.
For
example,
the
terms
“the
morning
star”
and
“the
evening
star”
have
the
same
extension
in
our
world
but
can
have
different
intensions
if
they
evoke
different
beliefs
or
concepts.
intension
as
a
separate
notion.
In
modern
semantics,
intensions
are
widely
used
to
model
meaning
in
linguistics,
philosophy
of
language,
and
cognitive
science,
helping
to
explain
phenomena
such
as
synonymy
across
contexts,
cross-world
variation,
and
the
handling
of
non-extensional
expressions.
an
unmarried
man,
while
its
extension
at
a
particular
world
is
the
set
of
men
who
are
unmarried
in
that
world.