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Funny Amphiboly #1
A newly married man asked his wife, “Honey, would you still have married me if my father hadn’t left me a fortune?” “Darling,” his wife replied sweetly, “I’d have married you no matter who left you a...
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Funny Amphiboly #2
The doctor said, “I can’t find the cause of your illness,” and then paused thoughtfully before continuing, “But I think it’s due to drinking.” “That’s okay, doctor,” the patient replied, “I’ll come...
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Funny Amphiboly #3
From headlines: “Iraqi Head Seeks Arms” “Study of Obesity Looks for Larger Test Group” “Two Sisters Reunited After 18 Years at Checkout Counter”
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Genus & Species Bonus
Lessons about genus and species charts often emphasize the capability of these charts to show relationships between terms (i.e. this is a kind of that). This is one benefit, but we should also note the...
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Why Define?
We define terms in order to make their meaning understood, of course. But we might ask, what does understanding the meaning of a term give us? Let’s dig a little deeper into this question. There are at...
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Abstract Concrete
One of my favorite college-level logic texts is The Art of Reasoning by David Kelley. In the chapter on “Classification” he teaches on genus and species, where he reminds us that the genus of a term is...
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Everything I say is a lie
A statement is a sentence that has a truth value, either true or false. Several types of sentences are not statements – questions and commands, for instance – because they do not have truth values....
View ArticleOn Relationships Between Statements
Mr. Nance, 1. Where does the A E I O come from for the four categorical statement types? These are simply the first four vowels in English. I have been told that A and I come from the Latin “Affirmo”...
View ArticleSubalterns?
Mr. Nance, Would you mind explaining the term “subalterns”? Thank you. “Subalterns” is another name for the relationship between two categorical statements of the same subject and predicate, with the...
View ArticleThe One Basic Verb & Past Tense
Mr. Nance, In the Intro Logic course, the answer guide shows that a past tense statement, “God created heaven and earth” was converted to the present tense, “God is the Creator of heaven and earth.” I...
View ArticleCategorical form & getting the subject right
Mr. Nance, In the Introductory Logic video Lesson 12, you write this sentence on the white board: “Some days the sun just doesn’t shine.” The first rule to put this sentence into the proper form...
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Logic and Biblical Ambiguities
Mr. Nance, On the Square of Opposition, the particular affirmative is “Some S is P” and the particular negative is “Some S is not P.” Why does the universal “All S is P” not have the contrary universal...
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Syllogism challenge
Some time ago on this blog, I challenged my readers to translate this syllogism from Quintilian into standard categorical form, and to determine its validity: “Virtue is the only thing that is good,...
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One Lesson Logic Students Must Learn!
The most important concepts to understand in Formal Logic is the concept of validity. All logic students should memorize and come to understand these three different (but related) ways of defining...
View ArticleA real-life enthymeme
Mr. Nance, An article included said of the following argument, “That’s a syllogism without a minor premise”: “[P]olitical decisions in the modern world often concern how to deploy science and...
View ArticleDistributed Terms
A term is distributed in a statement when the statement makes some claim about the entire extension of the term. For the four types of categorical statements, the highlighted terms are distributed, as...
View ArticleIllicit terms
In my last post I promised to explain the reasoning behind the rules of validity that relate to the distribution of terms. Recall that a term is distributed in a statement when it refers to the entire...
View ArticleUndistributed Middle
The second rule of validity that relates to the distribution of terms is this: A valid syllogism must distribute the middle term in at least one premise. This syllogism, for example, breaks this rule:...
View ArticleAnother rule of validity
Earlier I explained the fallacies of Undistributed Middle and Illicit Major/Minor. But what about the fallacies regarding the quality of the statements? One such rule of validity states, A valid...
View ArticleExclusive help
Unit 4: Arguments in Normal English in my Introductory Logic text is a difficult section, primarily because of the ambiguities within English. But if we want to be able to apply the tools for analyzing...
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