Questions tagged [logic]

For questions about logic, whether it concerns syllogistic logic, mathematical logic or the nature of logic itself.

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20 views

Need help to show the following is valid in SD+

I have to rely only on SD+ rules I use the Logic Book. Show that the following is valid in SD+ Derive Y=Z 1.~Y-> ~Z. Assume 2.~Z->~X. Assume 3~X->~Y. Assume I got Z->Y but am stumped on ...
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Has there been any philosophical interpretation (or application) of Stone lattices?

Stone lattices/algebras are Heyting (i.e. intuitionistic) lattices in which both laws of De Morgan hold, or equivalently, Heyting lattices in which also ~p \/ ~~p = 1. While these have been studied a ...
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I am stuck on SD+ style proof and need to know how to do it

I am using SD+. Most of the derivation has to be done using it I am finding this one tricky I request help or hints to solve it Derive L => H 1.~L v (~Z v ~U). Assume 2.(U & G) v H Assume 3.Z. ...
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Name for the concept where gluts are not (necessarily) a filter? (Or do gluts have to be a filter?)

In the following proof (which you'll excuse me, I hope, for giving only as slides/images), it is shown that (the relevance logic) R enriched with (A->B)\/(B->A) --enrichment which the authors ...
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Is there a “for dummies” construction of the valuation model of the relevance logic R from a De Morgan monoid?

I am confused how one gets the anti-chain preserving negation in Belnap-Dunn's FOUR, which by all accounts underlies their R (which adds implication), when R's valuation model is constructed from a De ...
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1answer
92 views

Is it there a “completely expressive” formal system / logic language?

I wonder whether it exists a formal system such that all (or a considerable number of) the others can be considered as a subsets or fragments of it. I would say that, for instance, First-Order logic ...
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7answers
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If I am unsure about the existence of morality, Am I morally obligated to find out the answer?

Since we do not know if morality has an independent existence, are we morally obligated to know if it exists?
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If A is true then B must also be true

What if in the statement, "If A is true then B must also be true," A & B are related but, "B must also be true," is not necessarily true because other possibilities exist? In ...
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Need to check to if my SL is correct for following problem

This is not homework . l do this for fun. I am 58. I graduated Concordia University in 1993 Problem comes from the Logic Book by Bergman pg 217 (17)c I want to see if my SL is correct. If civil ...
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56 views

Confidence margin for logical verification

I'm starting to read Wittgenstein and I keep circling around a problem, which I'll lay out with the following ideas: a. Logical space is the totality of external reality. b. A proposition is logical ...
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3answers
67 views

Could someone please write this argument's form

"No rock is sentient. Some mammals are sentient. Hence, no mammal is a rock." I wrote a form and it's apparently wrong, but I don't get how.
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How do you reduce repeated modality in S5?

Kenneth Konyndyk's Introductory Modal Logic claims (p. 55) that all formulas in S5 with a modal degree greater than 1 can be reduced to degree 1. By degree, he means the maximum number of modal ...
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I need help to Derive F & G

Derive F & G F=G. Assump. F v G. Assump. ? G. F & G. & I 1-? Should l use disjunction elimination or biconditional elim. next? I am flubbered Help
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2answers
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Formal logic - a priori or a posteriori

I am aware of the classical classification of logical calculus as apriori. I have also read pretty much anything I could get my hands on regarding "logic", including "New Essays on the ...
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4answers
124 views

What's the logical basis for Dunne suggesting that there need to be several dimensions of time in order to measure the speed of one's progress?

As a solution to the problem of the subjective passage of time, J. W. Dunne proposed an infinite hierarchy of time dimensions, inhabited by a similar hierarchy of levels of consciousness. Dunne ...
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How to apply Transdisciplinarity Logic to Truth Tables?

I've been having trouble trying to figure out Transdisciplinarity Logic. I have had little success while trying to research on my own, finding sources that are either too difficult to understand or ...
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What's the contrapositive of Duff's Test of Failure? [duplicate]

Isn't the contrapositive of 2 (Duff's test of failure) just 1? I can rephrase 2 below as 2.1. If the result didn't occur, would D regard himself as having failed (in his plan)? The logical ...
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7answers
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What logic comes closest to how humans think?

What logic comes closest to a descriptive model of human thought? It should be a non-monotonic logic. Sometimes a person can be convinced of a proposition by some evidence or argument, and then ...
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2answers
457 views

What's the logical difference between two sentences?

These are from an LSAT: No nonfiction book published by Carriage Book has ever earned a profit. Since Carriage Book earned a profit on every book it published last year, it clearly did not publish a ...
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62 views

Differences between “It is not the case that” and “not”? [closed]

Many articles say the following: Statement: "She is going to school." Negation statement: (1) "She is not going to school." or (2) "It is not the case that she is going ...
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2answers
40 views

What do you call a situation or case where a person say we are in a A XOR B situation when it's not?

What do you call a situation or case where a person say we are in a A XOR B situation when it's not? Let's say someone say either A is true or B is true, but not both A and B is true, but it's false. ...
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What is the difference between “satisfaction” and “verification”?

In Chalmers paper, "consciousness and its place in nature", he makes the following statement: We can say that if W (world) considered as actual makes S (a statement) true, then W verifies S....
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Why bother with anything else besides Aristotle's syllogistic logic?

Disclaimer: this a "devil's advocate's question", meaning I know a lot of the answer, but for the sake of playing the Q&A game, I won't self-answer right away. The main reason I'm ...
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6answers
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How would someone go about proving every known fact about the universe?

I will tell my wife known facts about the universe, and she will then tell me “well that could be fake how do we really know”. Even after explaining all the telescopes and other tools we have to find ...
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“You're not X, but… that says a lot”. Is this a fallacy?

I've seen this happen quite a lot in arguments about sensitive topics, such as racism, sexism or homophobia. When presenting a potentially controversial stance, someone might cushion the blow by ...
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2answers
61 views

Is the distinction between fact and opinion, and objectivity and subjectivity universal or cultural? [closed]

I noticed in certain cultures that I interact with here in Malaysia, it seems that the distinction between fact-opinion and objectivity-subjectivity is non-existent. Whereas in STEM and the scientific ...
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The specific term for a logical argument

Is there a specific term to use when someone is mocking you for something you have done in the past that they know was wrong only because they know now what happened, after the fact. You couldn't tell ...
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1answer
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What is the name of this fallacy: “A is B, therefore everything is B”? [duplicate]

We've all heard some form of the following statements: "I like cookies, therefore everyone likes cookies" "That plane is yellow, so all planes must be yellow." "I have come ...
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5answers
135 views

What's the relationship between physical and logical causation?

I have always presumed that logical causation - such as logical rules like the formation of a valid syllogism, or the law of the excluded middle - operate independently of physical causation. That is, ...
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2answers
61 views

Advanced logic books recommendations

I've studied from introduction to logic by Harry Jensler, so I'm looking for a more advanced and profound logic books any recommendations will be much appreciated, thank you in advance.
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3answers
159 views

Have I totally misunderstood conditionals all along?

I've been talking to a friend of mine about modus ponens (and modus tollens) and I'm wondering if I have totally misunderstood something fundamental about conditionals. Here are the two opposing ...
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3answers
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Confusing Conditional Statements

I've encountered many conditional sentences when doing LSAT questions. There are some type of conditional sentence which, unlike "if P, then Q", express some degree of uncertainty. For ...
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2answers
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what is the fallacy when someone misrepresents someone's views but acts as if they're not

For example, when Doctor X says "its bad when celiac compromised people eat gluten", then in an argument I say "its bad when everyone eats gluten, not just celiac compromised people. I ...
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2answers
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How to construct logic from nothing as a step by step procedure? [closed]

I am thinking of constructing logic from scratch. I tried the law of thought as a fresh start but not totally convinced this is a correct way for the following reason: if law of identity is the first, ...
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1answer
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Rejecting the principle that any proposition can be meaningfully negated

Is there a term for the meta-logical position that the negation of an arbitrary proposition is not a priori meaningful, or, in a stronger form, that some propositions lack negations? I was reading ...
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2answers
64 views

Does logic have to work out despite the subject? [closed]

I have a disagreement with someone about the logic of an argument. He says the statement "if it doesn't affect you, then you shouldn't care about it" is not an invitation to substitute "...
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1answer
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Non-Closed Logic? [closed]

Our logic is usually called "closed", i.e. if there's some formula/propostion F then its negation ~F is also a formula/proposition. (1) Could there be also a non-closed logic, i.e. a logic ...
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Why is “an invalid argument, the conclusion of which is a tautology” not possible? [duplicate]

A similar version of this question was answered before, (An invalid argument, the conclusion of which is a tautology) but I'm still a bit confused about why this is not possible. Like the other asker, ...
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Which field in the natural sciences always requires accurate and precise scientific instruments? [closed]

I am a high school student that believes as many others that natural sciences is an area of knowledge that is about reliable information. However, I see that scientific instruments play an significant ...
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4answers
249 views

Is a complete mathematical description of reality possible?

There are definitely states of systems(like mind) which are not quantifiable. For mathematics to work in principle, we need states which are quantifiable or measurable. So, does this go to show that ...
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0answers
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How can we trust second-order logic? [closed]

Hello Philosophy Stack Exchange, This is a question I originally asked on Mathematics Stack Exchange, but was encouraged to ask here. Unfortunately you cannot directly migrate to this site, so the ...
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0answers
69 views

What is the smallest theory formulated in a given first-order language? [closed]

I received an exercise question in my meta-logic course, which asks: "What is the smallest theory formulated in a given first-order language L? Provide an axiomatisation of this theory. What is ...
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2answers
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Logical fallacy in addition

Consider an example A A V ~B (addition) B > A It seems logically vaild . Now assume A is being apple and B is banana . So its equivalent **It's Apple It's apple or not banana If it's Banana ...
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The contraposition of this true statement does not seem to be true [duplicate]

-Every non blue thing I have observed in my room is non raven. The above is a true statement. But its contraposition does not seem to be: -Every raven I have observed in my room is blue. Please ...
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1answer
74 views

Resolve the contradiction/paradox [closed]

-We have observed that the color of a raven is black. -Every non-blue thing I have observed in my room is non-raven. -By inductive reasoning, every non-blue thing I will observe in my room is non-...
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5answers
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Winning Percentage Fallacy

Consider a combat tournament with a large number (sufficiently large that small sample size is not a problem) of combatants, in which each match is zero-sum and has a winner (there are no ties). The ...
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References on the analysis of “but”

I want to read philosophy papers that analyze the logical connective "but", and contrasts it with "and". I once read a paper that talked about this topic, but I can't find it ...
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Carnap's method of induction

Carnap provides a general understanding of symbolic induction, given as c(h, e)=r. c = degree of confirmation h = hypothesis e = evidence r = outcome What exactly is meant by Carnap's 'degree of ...
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Is there a taxonomy of disagreement types?

In philosophy, is there any type of taxonomy of types of disagreements? For example, I want students to look at varying takes on a subject. What I want them to focus on is, Why do such smart people ...
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Understanding Damore's statement about decreasing the false negative rate

At page 6 of his well-known memo, James Damore talks about the harm of Google's biases: Hiring practices which can effectively lower the bar for "diversity" candidates by decreasing the ...

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