Questions tagged [syllogism]

A syllogism is a form of deductive reasoning described by Aristotle containing two premises and a conclusion. Each of the premises and the conclusion contain a subject and a predicate.

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What is it called when the conclusion of one syllogism is inserted as the minor premise of a second?

As an example in Lewis's "Mere Christianity," he argues for objective morality with: Major: If you can judge one moral code (M1) to be better than another (M2) then objective morality exists. Minor: ...
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Is this argument about the disjuncive syllogism valid and sound?

If some arguments of the form disjunctive syllogism have false premises, then some arguments with false premises are deductively valid. Some arguments of the form disjunctive syllogism have false ...
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What are conditionally valid syllogisms? [duplicate]

I fail to understand why either S or M or P must exist for them to be valid. Such a constraint should apply to all premises, not just one and for valid syllogisms too. And this is about logical ...
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Is this the correct way to phrase a logical argument with multiple syllogisms?

I'm not familiar with phrasing arguments in the form of traditional logical syllogisms, so I'd like to ask if this formulation is correct, or if it can be expressed more concisely. Note, I'm not ...
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What's the difference between “All A are B” and “A is B”?

I'm having trouble catching the difference between these two forms. I tried to draw some Venn diagrams but it's not helping. "All A are B" means A is contained in B. Does "A is B" mean A is also ...
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Problem with existential import in syllogisms (Barbara)

For a syllogism in Barbara, why is it the case that All men are mortal. James’ son is a man. Therefore James’ son is mortal. assumes that James has a son but in the case of saying All ...
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How to solve this natural deduction problem?

This one is driving me crazy. I don't understand most keys for de morgan, modus ponens, etc, so please abbreviate if possible? EX: DM, MP, SIMP, HS, Conj, Imp (material Implication). Thank you anybody ...
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major/minor term of a syllogism when order of conclusion can be reversed

Consider: All ‘A’s are ‘B’s No ‘B’s are ‘C’s Is it not the case that the conclusion to this could either be: No ‘A’s are ‘C’s or No ‘C’s are ‘A’s ? Is it not also the case that the minor term ...
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Why is there an O type conclusion in modus celaront

Modus celaront is type logical syllogism. No reptiles have fur. (MeP) All snakes are reptiles. (SaM) ∴ Some snakes have no fur. (SoP) The conclusion is of a O type(Some .. are not ...). Why is ...
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Could the link between virtues and pleasures and pains in the third chapter of Nicomachean Ethics' book II be considered a hypothetical syllogism?

In the chapter 3 of Nicomachean Ethics' book II, Aristotle says: Again, if the virtues are concerned with actions and passions, and every passion and every action is accompanied by pleasure and ...
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Which logical fallacy is this: A is a C, B is a C, therefore A is a B?

Does this kind of logical fallacy have a name? Apples are fruit. Oranges are fruit. Therefore, apples are oranges. I'm guessing it's a particular kind of statistical syllogism?
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“Syllogisms which produce understanding”

I remember reading somewhere that the aim of Aristotle's Prior and Posterior analytics was to show which kinds of syllogisms produce understanding. I do not remember where I read this but I think it ...
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Do I have to use the BARBARA, CELARENT… etc?

My logic book is making me memorize the mnemonic that lists all these Latin names in order to remember valid syllogism forms, as well as how to reduce them into the first figure. My question is, do I ...
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Is this an example of Undistributed Middle?

Is this an example of Undistributed Middle? John is not a teenager, since all teenagers are impulsive, and John is not impulsive.
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What is an example of a monadic predicate calculus argument that cannot be represented by the 19 classical Aristotelian syllogisms alone?

While reading Wikipedia's description of the monadic predicate calculus, I read the following: Inferences in term logic can all be represented in the monadic predicate calculus. and Conversely, ...
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Does Hume reject the possibility of is-ought syllogisms?

Suppose the following syllogism: It is impossible for anyone to get X without him/her doing Y. It is possible to get X (by doing Y). I want to get X. Therefore I ought to do Y. There is, very likely,...
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syllogism, truth-functional, or neither?

I dreamed that John F. Kennedy was born in 1917, and everything I dream is true. Therefore, Kennedy was born in 1917. All horses are animals. Therefore, all heads of horses are heads of animals. If '...
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Modus Ponens as Substitute for Syllogism

This is a pretty basic question, but I haven't been able to find a clear answer in the various sources I've looked at, including the Kneales' chapter on conditionals in 'The Development of Logic'. ...
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Is the reiteration rule in formal logic begging the question?

Wikipedia defines "begging the question" as To "beg the question" is to put forward an argument whose validity requires that its own conclusion is true. I assume this is something Aristotle's ...
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Are syllogisms independent of humans?

For example, if "All a are b" and "All b are c" then "All a are c". To make this syllogism, does a conscious being need to exist? Or is it inferred from the sentences?
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Why does one negative premise suffice to imply a negative conclusion?

Capaldi PhD Columbia, Smit PhD Catholic University of Leuven. The Art of Deception (2007). Why's 2 true please? I can't intuit why, because 3 outwardly contradicts it. I prefer an intuitive ...
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how do people pick the letters for syllogistic logic problems?

I encountered the following argument while I was studying syllogistic logic from a book: All red cars kill papers, (premise) All cars that kill papers are beautiful, (premise) All red ...
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Why isn't the method of listing Terms in syllogisms widespread?

From: Philip Johnson-Laird BA PhD Psychology (UCL), Stuart Professor of Psychology Emeritus at Princeton. (Author isn't a logician.) How We Reason (1st edn 2008). p. 145. Is there a term for ...
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What is the nature of implication? [duplicate]

Or: how do statements follow from other statements? Consider: All turtles have shells (s1), Ricardo is a turtle (s2), therefore Ricardo has a shell (s3). Why does s3 follow?
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Does an implied premise mean a formal fallacy if used in deduction?

Let's just say we have an implied premise: 2.a Socrates is a philosopher (implied premise), but not explicit Then is the following a formal fallacy? Socrates is a man. All men are mortal. ...
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Is Euclid's syllogistic approach to proving mathematical theorems logically insufficient?

I think that deduction used in syllogistic systems, employing axioms and hence inferential conclusions i.e. theorems is rather weak, and cannot suffice for the robustness needed for proving ...
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How can I explain the distribution of an O proposition's predicate?

A student raised a tough question while I was teaching formal fallacies: couldn't the statement that "some cats are not tabbies" be made with confidence upon seeing a single cat that is not a tabby? ...
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How many valid categorical syllogisms are there?

Almost all contemporary logic books I have checked (as well as Wikipedia) agree that there are 24 conditionally valid logic syllogisms (Aristotle interpretation) 6 per figure and 15 unconditionally ...
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Does transposition of the premises preserve validity in categorical syllogisms?

This morning I've stumbled upon this doubt to which I couldn't find a clear answer. I intuitively myself that yes, it does preserve validity because as long as you don't change the premises the ...
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Is reduction to the absurdum to be considered a syllogism?

I was reading this article called Aristotle on the fourth figure. Thea author while exposing Aristotle theory of syllogism, identify 3 kinds of syllogisms which believes Aristotle to discuss: ...
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Is syllogism an inference rule?

I was reading Anthony Andres' article, "ARISTOTLE AND THE CONVENTIONAL LOGICIANS ON THE FOURTH FIGURE". The author explains why according to him the introduction of the fourth figure by his ...
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Reverse Conclusion of Hypothetical Syllogism

I am presented with an argument of form: If p, then q. If q, then r. Therefore, if r, then p. Does this structure have a specific title? I know that it is invalid, and am assuming that "reverse ...
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Why do we need Aristotle's theory of predication?

My question is about Aristotle's theory of predication. Why do we need it at all? I know it's intuitive to pick up something and say something about it like "S is P", but doesn't this lead us to ...
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Real World Example to break the logic of this Syllogism

I saw an example in a book talking about this setup: All 'P' are 'Q' All 'R' are 'P' All 'R' are 'Q' I am wondering if there are any real-life examples where the premises are true, but the ...
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Question about Syllogisms

Statements: I) No picnic is blades II) Some blades are CD's Conclusions: I) No CD is a picnic II) Some picnics are definitely not CD's Which one of these conclusions follow? I stated that ...
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Why do singular propositions have a universal quantity?

Why do singular propositions have a universal quantity? Singular propositions like Amy is woman. Why do we treat them as if they referred to classes of things?
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Are “All A is B” and “If A then B” always logically equivalent?

Will "All A is B" always imply "If A then B?" If so, can we say that the following follows the form of Modus Ponens? All dogs are mammals. Toby is a dog. So, Toby is a mammal. Can I rewrite ...
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Is there a name for a fallacy wherein it is assumed either someone is lying or their assertion is true?

I'm hoping to find a name already in somewhat common usage for a fallacy of the following form: A person claimed X. Therefore either X is true or the person is lying. I've seen this fallacy ...
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Does this syllogism by Russell show that Aristotelian logic doesn't work?

I have been reading through Hurley's A Concise Introduction to Logic, and I just finished reading the chapters about categorical syllogisms. While prodding around Wikipedia looking for some ...
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Is restatement true in syllogism?

Statement : All A is B Conclusion : All A is B. Does this conclusion follow?
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Is there a way to generate the 24 valid syllogisms in term logic?

There are four qualifiers in term logic, organized according to two distinctions: particular/universal (some versus all) and affirmative/negative (permitting none and not all). There are 256 ...
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Syllogism Problem Assistance

I have problem with the following syllogism. Some A are B All B are C ———————————— Some B are C Some A are C I think both are correct answers while my book says that the only correct answer is "some ...
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Categorical syllogism question

I have trouble understanding this syllogism. Given: Some P are not G No O are P My conclusion is : Some O are not G In this online exercise I did my answer was incorrect and that website does not ...
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Do premises in modus tollendo tollens arguments require greater certainty than others?

In a standard syllogism, the two premises of the argument are independent of each other, so all extrinsic warrant being equal, the argument will prove the conclusion to be probable if and only if... ...
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Only valid syllogisms are syllogisms?

If I have an invalid syllogism, it can still be considered a syllogism, right? Example: All A is B All B is C All C is A It is invalid. But it's still syllogism? (I know that may seem obvious, but ...
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“All men are mortal, Socrates is a man, therefore, Socrates is mortal” original quote

Where the syllogism "All men are mortal / Socrates is a man / Therefore, Socrates is mortal" first appeared?
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Wendelin, Marcus Friedrich - Logicae Institutiones tironum adolescentum

where can I find an English translation of this book? Also, in it he talks about 12 pairs of term categories. which are really 21 (9 actual pairs and 3 "double sided" categories): he writes - De ...
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Why are these formulas not well-formed in syllogistic logic?

I'm studying formal logic, and I get stuck in the beginning. I'm trying to do easier translations in syllogistic logic. I'm using Gensler book "Introduction to Logic". They say that this examples ...
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In modern logic, why does “All S is P” contradict “Some S is not P”?

In modern logic, the existential import is removed from universal statements. So All S is P may still be true if there is no S at all. Contradictory statements must have opposite truth values. Why ...
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help with answering the set of statements : All cats are lions, some lions are mice, all mice are giraffes

Consider the three statements A,B and C to be true even if they are different from the commonly known facts I drew two euler diagrams for this and concluded that conlusion II and IV follows and ...