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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How do I use the “Barbara, Celarent, … etc.” mnemonic?

Medieval logicians memorized this most famous logic mnemonic: Barbara, Celarent, Darii, Ferio ← direct first figure Baralipton, Celantes, Dabitis, Fapesmo, Frisesomorum ← indirect first figure Cesare,...
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Why is the darapti syllogism invalid?

I found the following exposition of darapti on wikipedia: All squares are rectangles. (MaP) All squares are rhombuses. (MaS) ∴ Some rhombuses are rectangles. (SiP) As far as I can see, this is ...
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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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Syllogistic Logic: Negation of a Categorical Proposition?

I am beginner of logic, and am writing an introduction to logic for a math book. I am of the impression that the three main areas of logic to explain are (in order) syllogistic logic, sentential logic,...
654 views

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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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 ...
278 views

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: ...
445 views

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 ...
455 views

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 ...
253 views

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 ...
2k views

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 ...
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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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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 ...
746 views

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. ...
314 views

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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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 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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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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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 ...
66 views

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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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 ...
271 views

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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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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Are analogical middle terms sufficient for a valid demonstration?

William A. Wallace, O.P., in “Thomism and the Quantum Enigma,” The Thomist 61 (1997): 455–468, claims that analogical middle terms are sufficient for a valid demonstration and that this is a ...
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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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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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“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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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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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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How do affirmative premises assert class inclusion rather than class separation?

Source: A Concise Introduction to Logic (12 Ed, 2014), by Patrick J. Hurley. Please observe my amelioration (and so change) of Hurley's notation; I use MIN, MAJ, and MID to abbreviate the Minor, Major,...
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Is “only A are B” the same as “all B are A”?

I have two syllogisms which I think are pretty similar. Correct me if I am wrong but I believe "Only A are B" is the same as "All B are A". Only A are B (Can be rewritten as "All B are A") Only B are ...
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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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Is restatement true in syllogism?

Statement : All A is B Conclusion : All A is B. Does this conclusion follow?
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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 ...
322 views

Particulars in a conditional syllogism

I have the following syllogism: Should all goods come from virtue, no evil man possesses the good. Some evil men possess the good. Therefore, some goods do not come from virtue. I ...
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Representation of Categorical Syllogism in Symbolic Logic

How would I represent a AAA categorical syllogism with symbolic logic?
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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? ...
154 views

What is a predicate according to Aristotle's Organon?

There is of course predicate as in predicate logic; but I'm asking about the notion in Aristotle's Organon. Consider the proposition: Socrates is a man. Man is a universal, Socrates is a ...
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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 ...
76 views

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 ...
127 views

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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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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In a Syllogism with an I Proposition as the conclusion, why must both premises be affirmative?

Source: A Concise Introduction to Logic (12 Ed, 2014), by Patrick J. Hurley [p 286:] Rule 1: The Middle Term Must Be Distributed at Least Once. [p 288:] Rule 4: A Negative Premise Requires a ...
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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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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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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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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 ...
153 views

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,...