Questions tagged [propositions]
The propositions tag has no usage guidance.
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Propositions as set of possible worlds in FOL
In possible world semantics for propositional calculus, possible worlds are usually taken to be models for propositional formulas (the set of valuations in which a certain formula is true)
In first ...
2
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4answers
193 views
What is my fallacy? LSAT Reasoning Question: Titanium Ink
I have a question regarding an LSAT Reasoning question and it drives me crazy
Question is:
Until recently it was thought that ink used before the sixteenth century did not
contain titanium. However, ...
0
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0answers
25 views
Does Procedural/Non-propositional Belief Exist?
In the SEP article on knowledge-how, procedural knowledge is said to be "the knowledge that is manifested in the performance of a skill", whereas declarative/propositional knowledge is "...
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0answers
66 views
Can one only believe in perceptions?
In the following example provided by SEOP, Kai is said to believe a proposition:
for example, when Kai reads that astronomers no longer classify Pluto as a planet, he acquires a new belief (in this ...
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3answers
127 views
Is “thoughts exist” a synthetic a priori statement?
I'm working off of Kant's conception of analytic/synthetic and a prior/a posteriori judgements.
The definition of "thoughts" does not subsume their existence. That is, it is logically ...
-1
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1answer
157 views
When is a wish not a proposition?
Consider these sentences:
S1. Would that Los Angeles were not that far away.
S2. I really wish Los Angeles were nearer to New York.
S3. I wish that Los Angeles were not that far away.
S4. It is going ...
-1
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1answer
166 views
what is meaning of accessibility of possible worlds?
I have a question about the notion of possibility in modal logic.
There are systems and worlds with this notion.
They say that a world w1 is accessible to an other world w2 if and only if for any true ...
2
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2answers
100 views
Can the word “probably” be used in a proposition? (logic)
I'm interested in applying logic to day-to-day reasoning. The problem is that formal logic seems really restrictive to limit inductive arguments to be only universal ("all swans are white"). Few ...
3
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2answers
105 views
Analyticity and a priority
(1) Every bachelor is unmarried.
I know this is one of the most famous examples (intensionally) denoting analytic and a priori propositions. No problems yet.
(2) Every apple is a fruit.
This one ...
2
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1answer
47 views
A set of three statements, of which only two at a time can be true: is there a specific term for this type of combination game?
Here's two examples of what I'm talking about
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An ideal citizen would be smart, ethical and politically engaged.
However, what usually happens in reality is this:
If they're smart ...
4
votes
4answers
237 views
Can one have propositional knowledge without knowing the corresponding proposition?
The concept of propositional knowledge -- knowledge that one has through holding a justified belief in a proposition that states a fact -- is a foundational one in epistemology (for example, it is ...
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2answers
199 views
Confused about the answers to two logic problems
True or False? If monkeys can fly, then 1 + 1 = 3.
What is logically equivalent to all x (p(x) + ~q(x))?
For the first one I think it is False.
0
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1answer
789 views
How to make the statement “If A or B then C” More Rigorous?
Suppose that I say the following,
If A or B then C
It is clear what happens if only A is true, if only B is true, or if neither A nor B are true.
However, what happens if both A & B are true? ...
2
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0answers
53 views
How did Aristotelian logic view this?
I am very interested in the logical aspect of Aristotelian philosophy, especially how it was used by al Farabi and Ibn Sina in explaining understanding and breaking this complicated process down ...
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0answers
27 views
partial fictionalism about propositions
One theory of propositions is that they're "useful fictions." However, this faces the formidable objection that fictionalism makes it hard to explain how something fictional can tell us about the ...
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0answers
112 views
If logical propositions aren't tautologies (a la Wittgenstein), then what could they be?
This is a historical question about philosophical views. I believe I understand the claim made by Wittgenstein and others that logical propositions are tautologies. I'd like to know what other views ...
6
votes
1answer
247 views
Is the principle of non-contradiction self-evident?
The principle of non-contradiction is that contradictory propositions cannot both be true, e. g. the two propositions "A is B" and "A is not B" are mutually exclusive.
However, whenever something is ...
2
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1answer
389 views
How does a truth tree provide positive and negative effect tests for implication?
I'm trying to prove that the truth-tree method can be used to give a positive effect test for implication, and a negative effect test for non-implication. I've been given the fact that The truth-tree ...
2
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0answers
103 views
Why don't two equivalent propositions contribute to the same semantics?
We often have 2 propositions that have the same truth table, in that they are true and false given the same conditions.
Nevertheless, we still feel as though there different semantics (i.e meaning..),...
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3answers
145 views
On Truth and Lying
If A, consciously, reports false data to B, and B (or anyone else) has no way to verify, then no one can make the statement, "A lied". So, there exists no such person with respect to whom A lied.
...
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2answers
686 views
Existential import: in logic, do propositions default to true or false when objects in them do not exist?
In this hypothetical:
Firefighters always tell the truth, while politicians always tell lies.
Suppose three people, who are either a mix of firefighters and politicians, all politicians, or all ...
2
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5answers
2k views
Why is questioning everything around us so important?
I've heard something disturbing from my friend. He said he's grateful to his father because his father taught him to question everything that was around us.
Why is this so important?
5
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3answers
185 views
How does one judge “complexity” of assumptions for the purposes of “best explanation”?
The context for this question is from assessing theological arguments from the point of view of 'inference to the best explanation'.
In philosophy (and science), we may wish to argue that some ...
2
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3answers
55 views
Understanding multiple values in a single cell of a truth table (P v ~Q) as (1 1 0 1) when P and Q are 1
This might seem basic to most here but I am struggling with a truth table for a disjunct. As I am looking at it further, I actually think the issue I am struggling with how to interpret truth values ...
1
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1answer
180 views
Into what category does following view place me in moral philosophy?
At first, I believe the statements like "Pete is wrong" and "Mike acts in a bad way" have some cognitive value. At first glance, this puts me to ethical cognitivism.
But at the same time I think the ...
4
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1answer
687 views
The nature of elementary propositions in the Tractatus
So all complex objects in the world are, at the most fundamental level, made up of simple un-analysable objects which are denoted by 'names'.
Combinations of simple objects constitute 'states of ...
5
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1answer
960 views
Making 'sense' of Wittgenstein's senselessness / nonsense distinction in the Tractatus
For this question I'm just considering Wittgenstein's theory at the time of the Tractatus.
As far as I know, for Wittgenstein:
Meaning - The object denoted by a word (i.e. referent).
Sense - The ...
1
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2answers
452 views
Confusion about an implication's contrapositive
I just begin learning propositional logic and find a little bit confused when trying to translate the contrapositive of an implication back to the English language.
For example, I have an ...
2
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0answers
236 views
Russell on Negative Facts
Okay. I am reading Russell's paper "On Propositions: What They are and How They Mean". Since the truth or falsehood of a belief depends upon a fact to which the belief "refers", and propositions are ...
2
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3answers
173 views
Problem with propositions about future
I have some questions about propositions of future like “tomorrow, there will be rain” or “you won’t go to school tomorrow”
1) Are there certain truth values of future propositions? For example, ...
2
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5answers
1k views
In propositional logic, why can a FALSE antecedent of conditional be simplified to TRUE?
Please help me formulate my sentences/thoughts here into logical jargon and solve Case 2 below.
Why does the truth table for an implication → look like this:
| p | q | p → q|
| T | T | T |
| T | ...
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0answers
349 views
Create a statement in propositional logic. This statment must have 2 attributes. (The attributes are specified in the top header)
The following are the 2 attributes: (1) This statement claims the statement after it is true. (2) This statement cannot be not true.
This statement would achieve these 2 attributes through its wording....
3
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1answer
228 views
What are the rules for a zero-premise derivation involving disjunctions?
I'm having trouble with the following zero-premise deduction that involves two disjunctions:
The solution seems simple, but I'm unsure of how to proceed with the two disjunctions. If it were just ...
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2answers
2k views
Definition of proposition
The term proposition has a broad use in contemporary philosophy. It is used to refer to some or all of the following: the primary bearers of truth-value, the objects of belief and other "propositional ...
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1answer
370 views
How is this premises and conclusion to refute Searle's CR experiment?
So I've been digging into this topic for days now. I've gone through his paper and also some threads here, which I found were very helpful.
I came up with these premises and following conclusions in ...
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3answers
419 views
Is there a logical system that accounts for cause and effect relationship?
The reason I ask is because of the ambiguity of some statements when the conditionals of a condition are not referenced by tense i.e time. For example, in the Cognito Ergo Sum 'I think therefore I am',...
4
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1answer
91 views
Are analytic propositions always vacuously true?
In a possible world where there are no bachelors is the proposition "bachelors are unmarried" vacuously true? Or is it tautologically true and you would then need to quantify bachelors as "all ...
1
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1answer
106 views
Can we know a predicate without a subject, non-propositionally? [closed]
Can we have non-propositional knowledge, for example knowledge of a predicate without a subject? I think an example would be: only this is now, which uses indexicals. I'm asking because I wonder ...
3
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2answers
500 views
Implication Introduction formulated as a theorem?
While making a list of the rules of inference for my math students, I came across this list on Wikipedia:
I noticed a pattern: for every introduction rule, there seems to be an elimination rule, and ...
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1answer
864 views
Why is the statement false: If (A⊃B)∨(A⊃C) is true, then A implies either B or C
I'm reviewing my previous exams for the final, and the only two true or false questions that confuse me are:
If (A⊃B)∨(A⊃C) is true, then A implies either B or C.
(P⊃Q)∨(P⊃~Q) means P⊃(Q∨~Q).
The ...
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3answers
1k views
Intuitively, why are Universal Statements true in the Empty Universe?
Source: p 165. Sweet Reason: A Field Guide to Modern Logic (2010 2 ed) by Henle, Garfield, Tymoczko.
I read this on Math SE; please advise if it pertains to my simpler question.
One property of ...
4
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1answer
215 views
Why isn't “I am Bill” a proposition?
In fleshing out the traditional definition of omniscience, William Lane Craig distinguishes between propositional knowledge and non-propositional knowledge, claiming that to be omniscient is to know ...
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0answers
54 views
Can the material conditional be used in other situations?
Can the material conditional in classical logic (e.g. propositional logic or predicate logic like first-order logic) be used to reason about propositions that are not factual? E.g., using a ...
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2answers
283 views
can we know whether the self-referential statement: “It's not possible to deduce whether P1 is true or false” is undecidable?
Update: Simple concise version
Thanks to Nick R for pointing in the right direction.
The statement P0: "this statement is false" is undecidable.
The statement P1: "this statement is undecidable" is ...
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1answer
145 views
Does the existence of the proposition require language to be referential?
If we grant that there is a proposition wherein something meaningful is being asserted, does that require us to think of language as essentially representative in some way?
If language didn't contain ...
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1answer
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What are factual propositions?
I've been reading up on epistemology, after having studied a bit of logic. Given that, I am in a good (or at least better) position to understand a proposition, and it's properties. One such property ...
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4answers
657 views
Truth Value of Sentences Containing Logical Contradictions
Do propositions containing logical contradictions have truth values, or are they meaningless? For example:
A) Some married bachelors exist.
B) 95% of married bachelors live in Maryland.
C) ...
3
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1answer
152 views
Wittgenstein and Picturing Relationships
I've been listening to BBC's "In Our Time" on Wittgenstein here, but I can't seem to understand why Wittgenstein thought that "a proposition can't picture the pictorial relationship." One of the ...
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7answers
2k views
How do you prove that this is a tautology?
((p->q) and (r->s) and (p or r)) -> (q or s)
How would you prove that this is a tautology? Using natural deduction?
My attempt on this question is the following.
Since a tautology means W entails ...
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1answer
109 views
Is what makes a proposition true only determined by its referent?
I was wondering if it is trivial that when the content of a belief can be given or "determined" by mind independent reality, the belief is "about" mind independent reality.
I think that the content ...
