Semantics - Basesproduced.com
Semantics - Basesproduced.com
Semantics - Basesproduced.com
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<strong>Semantics</strong><br />
April 5, 2012
The Last Details<br />
• <strong>Semantics</strong>/pragmatics homework will be posted after<br />
class today.<br />
• Will be due next Thursday<br />
• Future plans:<br />
• Today: semantics<br />
• Tuesday of next week - wrap up semantics<br />
• Thursday: some <strong>com</strong>ments on language preservation<br />
• With a guest speaker!<br />
• + an opportunity to ask some review questions<br />
• <strong>Semantics</strong> homeworks will be graded by Monday of final<br />
exam week (the 16th)
Moving On<br />
• There are several different ways to study meaning in<br />
language:<br />
1. Pragmatics<br />
The meaningful use of linguistic expressions in<br />
conversation and discourse.<br />
2. Compositional <strong>Semantics</strong><br />
How the meaning of phrases and sentences is built up<br />
from the meanings of individual words.<br />
3. Lexical <strong>Semantics</strong><br />
The meaning of individual words, and how they’re<br />
related to one another.
Here’s a question…<br />
• What is “meaning”?<br />
• No, really. What is it? Any ideas?<br />
• The meaning of “meaning” seems to be very <strong>com</strong>plex<br />
and hazy.<br />
• For today, we’ll try to figure out what “meaning” means<br />
for a small, simple set of data and then work from there.<br />
• We’ll be doing <strong>com</strong>positional semantics.<br />
• …and we’ll focus on the literal meaning of linguistic<br />
expressions, for now.
Possible Worlds<br />
• Consider this idea: we live in one of many possible<br />
different worlds.<br />
• There are certain true statements we can make about the<br />
world in which we live. For instance:<br />
If you jump up, you fall down.<br />
The sun is about 93 million miles away.<br />
Mars is a planet.<br />
It’s chilly outside.<br />
I am teaching linguistics 201.<br />
Hobbits do not exist.
Possible Worlds<br />
• In other possible worlds, different statements might be<br />
true. For instance:<br />
If you jump up, you fly off the surface of the Earth.<br />
The sun has be<strong>com</strong>e a black hole.<br />
Pluto is a planet.<br />
The weather in Calgary is always nice.<br />
I am married to Scarlett Johansson.<br />
A hobbit named Frodo stole my wedding ring.
What is truth?<br />
• How do we know that some of these statements are true,<br />
while others are not?<br />
• What does it mean for something to be true?<br />
• Let’s consider the philosophical question this way:<br />
• What sorts of things can be true?<br />
• (hint: think in syntactic terms)<br />
• Can a noun be true? A verb? An adjective?<br />
*Is it true that dog?<br />
*Is it true that escape?<br />
*Is it true that happy?
What is truth? (part 2)<br />
• How about verb phrases or noun phrases?<br />
*Is it true that {make copies}?<br />
*Is it true that {destruction of the city}?<br />
• Whole sentences?<br />
Is it true that Pluto is a planet?<br />
• Declarative sentences can be true.<br />
e.g., “Hobbits do not exist.”<br />
...as opposed to interrogative or imperative sentences<br />
(questions or <strong>com</strong>mands)
A Theory of Truth<br />
• Declarative sentences are also known as propositions.<br />
• Let’s assume that a proposition is true if:<br />
• the information it imparts about the world is actually the<br />
way the world is.<br />
• A philosophical definition:<br />
• truth is the correspondence of propositions to facts.<br />
• This is called the correspondence theory of truth.<br />
• Q: What kind of information can a proposition provide<br />
about the world?
Subjects, Predicates<br />
• Let’s consider declarative sentences with this form:<br />
S → NP VP<br />
• We already know that the NP is called the subject.<br />
• Let’s call the VP the predicate.<br />
• Subjects refer to “persons, places or things”.<br />
• Predicates (roughly) describe relationships between the<br />
persons, places or things.<br />
• Subjects are what’s in the world;<br />
• Predicates are “the way the world is.”
This is the world.<br />
One Possible World
One Possible World<br />
Mars Venus Pluto<br />
Earth<br />
Mercury<br />
Neptune<br />
Jupiter<br />
Uranus<br />
Saturn<br />
The Moon<br />
The Death Star<br />
This is the world.<br />
These are different things<br />
in the world.
One Possible World<br />
Mars Venus Pluto<br />
Earth<br />
Mercury<br />
Neptune<br />
Jupiter<br />
Uranus<br />
Saturn<br />
The Moon<br />
The Death Star<br />
is a planet<br />
this is a predicate
Another Possible World<br />
Mars<br />
Venus<br />
Earth Pluto<br />
Mercury Saturn<br />
Jupiter<br />
Neptune<br />
Uranus<br />
The Moon<br />
The Death Star<br />
is a planet<br />
this is a predicate
Another Possible World<br />
Mars<br />
Mercury<br />
Earth<br />
Jupiter<br />
Venus<br />
Saturn<br />
The Moon<br />
is a planet<br />
this is a predicate
Reference<br />
• Note that the expression “Jupiter” is not the planet Jupiter<br />
itself;<br />
• It’s just a linguistic convention we can use to refer to<br />
the actual thing.<br />
• The actual thing (in the world) is the referent of the word<br />
“Jupiter”.<br />
• Another example:<br />
“Barack Obama”<br />
expression<br />
referent
Reference: Another Example<br />
“The Mona Lisa”<br />
“La Joconde”<br />
“La Gioconda”<br />
expressions<br />
referent<br />
Remember: languages can be arbitrary.
Extension<br />
• A predicate is a set of referents in some possible world.<br />
• This set of referents is known as a predicate’s extension.<br />
Mars Venus Pluto<br />
Earth<br />
Mercury<br />
Neptune<br />
Jupiter<br />
Uranus<br />
Saturn<br />
The Moon<br />
The Death Star<br />
is a planet
Finding the Truth<br />
• With this framework in place, we have a formula for<br />
figuring out whether or not a proposition is true.<br />
• Formula: a proposition is true if the referent of its<br />
subject is contained in the extension of its predicate.<br />
• Consider the proposition: Pluto is a planet.<br />
• The subject’s referent is:<br />
• The predicate’s extension includes:<br />
• Therefore, “Pluto is a planet” is a false proposition.
Truth Values<br />
• In any possible world, a proposition may have one of two<br />
different truth values.<br />
• “Pluto is a planet” may be false.<br />
or<br />
• “Pluto is a planet” may be true.<br />
• We can calculate a proposition’s truth value when we<br />
know:<br />
• what its subject refers to<br />
• the extension of its predicate<br />
• ...in some possible world
More Expressions<br />
• Note: a number of different expressions can refer to the<br />
same thing in the world.<br />
The 43rd President of the United States<br />
The former owner of the Texas Rangers<br />
George H.W. Bush’s oldest son<br />
“43”<br />
“Shrub”<br />
• George W. Bush is the referent of all of these expressions.
There is no Santa Claus<br />
• Note that there are some expressions which have no<br />
real-world referent:<br />
Santa Claus<br />
The Easter Bunny<br />
A Unicorn<br />
Frodo Baggins<br />
The King of the United States<br />
• Q: Are these meaningless expressions?
Sense<br />
• Expressions like “The President of the United States”<br />
have different referents in different possible worlds.<br />
• Consider the referents of this expression in three<br />
possible (past) worlds:<br />
1805: Thomas Jefferson<br />
1905: Teddy Roosevelt<br />
2005: George W. Bush<br />
• Idea: the sense of an expression is the set of its referents<br />
in all possible worlds.<br />
• (Note: the textbook refers to the sense of an expression<br />
as its “intension”.)
Another Example<br />
• From 1979-1999, the expression “8th planet from the<br />
Sun” technically referred to Pluto.<br />
• In all possible worlds, however, the expression “8th<br />
planet from the Sun” refers to:<br />
• the planet which is eighth-most distant from the Sun
Meaning<br />
• Corollary: expressions like “Santa Claus” are not<br />
meaningless, even though they have no referents in this<br />
world.<br />
• Their meaning, or “sense”, is their set of referents in all<br />
possible worlds.<br />
• ⇒ You can talk about Santa Claus because you know<br />
what the world would be like if he existed.
Truth Conditions<br />
• Within this framework, we can now make the following<br />
claim:<br />
• The meaning of a proposition is the set of all possible<br />
worlds in which that proposition is true.<br />
• Another way of saying the same thing:<br />
The meaning of a proposition is the set of conditions in<br />
which that proposition is true.<br />
• I.e., its truth conditions.<br />
• When you know the meaning of a proposition, you know<br />
the conditions under which it can be true.
Rehashed Ad Nauseum<br />
• Check out this possible world:<br />
“It can only be the thought of verdure to <strong>com</strong>e, which<br />
prompts us in the autumn to buy these dormant white<br />
lumps of vegetable matter covered by a brown papery<br />
skin, and lovingly to plant them and care for them. It is a<br />
marvel to me that under this cover they are labouring<br />
unseen at such a rate within to give us the sudden<br />
awesome beauty of spring flowering bulbs. While winter<br />
reigns the earth reposes but these colourless green ideas<br />
sleep furiously.”<br />
--C. M. Street
Compositionality<br />
• By the way:<br />
The idea that the meaning of a sentence can be<br />
calculated from the meaning(s) of its parts is the<br />
principle of <strong>com</strong>positionality.<br />
• Consider this sentence:<br />
The President of the United States is a white male.<br />
• Is this true? How do you know?<br />
• How about this sentence:<br />
Santa Claus is a white male.
Types of Sentences<br />
• Propositions may be distinguished on the basis of the<br />
kinds of worlds in which they may be true.<br />
1. Synthetic propositions may be true or false,<br />
depending on the state of affairs in the world.<br />
2. Analytic propositions are always true, no matter<br />
what the state of the world.<br />
3. Contradictions are always false, no matter what the<br />
state of the world.<br />
• Quick Write check.
Meaning Summary<br />
• Reference: the actual thing in the world an expression<br />
picks out.<br />
• Extension: a set of referents (= a predicate) in some<br />
possible world.<br />
• Sense: what an expression refers to in all possible worlds.<br />
• Truth: a proposition is true if the referent of its subject is<br />
contained in the extension of its predicate.<br />
• Meaning:<br />
• The meaning of a proposition is the set of conditions in<br />
which that proposition is true.<br />
• Truth conditions