Phil1001__Problem_Set_11___Answer_Key
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University of Minnesota-Twin Cities *
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Course
1001
Subject
Philosophy
Date
Apr 3, 2024
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Uploaded by KidBraveryLemur17
Phil1001: Introduction to Logic
Name:
Fall 2021
Group:
Problem Set 11: Sentences of FOL – Answer Key
Due: December 6, 2021 at 11:59pm
These are example solutions! With the exception of (3), your solutions may differ significantly.
Ask your TA if you are uncertain of the quality of your answer.
1. (4pts)
Definite Descriptions.
Provide a translation into FOL of the following two definite
description. Make sure to provide a translation key. (Reference: Ch. 27)
a.
The President of the University of Minnesota has a Philosophy B.A.
∃
x
((
U
(
x
)
∧ ∀
y
(
U
(
y
)
→
x
=
y
))
∧
P
(
x
))
U
(
x
)
: x is President of the University of Minnesota
P
(
x
)
: x has a Philosophy B.A.
b.
The world’s oldest living llama was born in 1994.
∃
x
((
L
(
x
)
∧ ∀
y
((
L
(
y
)
∧ ¬
x
=
y
)
→
Y
(
y, x
)))
∧
B
(
x
)
L
(
x
)
: x is a living llama
Y
(
x, y
)
: x is younger than y
B
(
x
)
: x was born in 1994
(…his name is Ramadan’s Arapahoe Gold aka ‘Rapper’ You can see him with his llamadad
here.)
2. (3pts)
Ambiguity
The following sentence is ambiguous. Give two possible, logically distinct
symbolizations of this sentence in FOL. Make sure to include a translation key. Additionally,
explain
how these two symbolizations are distinct.
Mari saw only red apples at the grocery.
M
(
x
)
: Mari saw x
G
(
x
)
: x was at the grocery
R
(
x
)
: x is a red apple
A
(
x
)
: x is an apple
D
(
x
)
: x is red
∀
x
((
M
(
x
)
∧
G
(
x
))
→
R
(
x
))
The only things that Mari saw at the grocery were red apples. (Ie, they were out of literally
everything else).
∀
x
(((
M
(
x
)
∧
G
(
x
)
∧
A
(
x
))
→
D
(
x
))
The only apples Mari saw at the grocery were red ones. (Ie, they were out of green, gold, and
pink apples.)
3. (1pts)
What are the four components of an interpretation?
1. A specification of the domain
2. Extension of any predicates we are considering
3. Assignment of names we are considering to objects in the domain
4. Truth values for any sentence letters we are considering.
4. (2pts)
Extensionality.
In the hit young adult novel and film series
Twilight
(yep.), there is
a love triangle between Bella Swan, Edward Cullen, and Jacob Black. Using either ordered
pairs or a graphical representation, describe your best guess at what that love triangle looks
like (Reference:
§
29.3). Who loves who? Who doesn’t? Then, describe your representation
in English.
(Note that this will
NOT
be graded on the “correctness” of your Loves relation as a representation
of the characters in Twilight. I don’t remember, and I refuse to either look it up myself or make
you look it up.)
Here’s the beginning of an interpretation to get you started:
domain: characters in
Twilight
L(x, y):
x
loves
y
b: Bella
e: Edward
j: Jacob
L
(
x, y
) :
< b, e >, < j, b >, < e, b >, < b, j >
This “loves” relation describes a love triangle in which Bella loves both Edward and Jacob, and
both of them love her. Neither loves one another and none of these people love themselves.
2
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