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Please begin with an informative title:

Thanks to everyone who responded to my proposal for a logic series!

I welcome any input about what times & days would be best to post the installments. Right now, I'm thinking Monday, Wednesday, & Friday afternoons or evenings, though as more complex subjects come up — or other business unexpectedly eats my time — I may subtract, add, or shift days "sideways" a bit.

At any rate — following the order in my notebook — I'll begin the 1st of several discussions of informal fallacies past the Kos Wingding.


You must enter an Intro for your Diary Entry between 300 and 1150 characters long (that's approximately 50-175 words without any html or formatting markup).

Last time, in my "sample lesson", I gave the basic definitions of propositions & arguments. Here they are again [UPDATE: Definition of "proposition" simplified per suggestion from commenter ends with space]:

A proposition is a statement that may be either true or false.
An argument is a group of propositions that may be either valid or invalid. An argument typically has premises & a conclusion.
(Feel free to review the above link to the diary if you need examples & further explanation.)

Today I will begin the 1st of a series of diaries on informal fallacies.

Basically a fallacy is any kind of mistake in logic. Mind you, nobody has ever made a complete list of all possible ways that someone can think wrongly, so only so much listing & classifying of fallacies can be done. None the less, logicians generally divide fallacies into formal, those which make mistakes in terms of truth & falsehood of propositions, usually through invalid argument forms, & informal, those mistakes that arise from unclear language (ambiguity) or language that's beside the point (relevance).

This diary will focus on several fallacies of ambiguity. (I'll include some of their alternative names so as to help you research these on your own. I prefer to use everyday English forms that I find easy to remember & relay to others, but many textbooks traditionally use Latin & Greek names or potentially obscure technical terms.)

Emphatic Ambiguity (Accent).
Many mistakes can result from placing stress on the wrong part of a statement, or for that matter leaving the appropriate stress unclear. This is especially true for members of an online community, since they cannot see each others' facial expressions or hear each others' voices giving the precise intonation that shows that this is the proper sense which was meant. (An old example: Think how the saying "Woman — without her, man would have nothing!" looks without punctuation.)

Grammatical Ambiguity (Amphiboly).
Sometimes the way a particular statement is phrased makes its precise meaning difficult to figure. (Shakespeare readers will remember "No man of woman born shall harm Macbeth" — & Greek historian Herodotus relays this from the Oracle at Delphi: "If Croesus attacks the Persians, he will destroy a great empire." (If only he knew which one...) Also, what does someone mean who says "I hope this diary gets precisely the attention it deserves"?)

Lexical Ambiguity (Equivocation).
Certain words, whether due to being homophones or having more than 1 popular meaning, can be confusing as well. (Classic humorous illustration: "Some cats chase bugs. My cat chases bugs. Therefore, my cat is some cat!)

Well, I think that will do for now. Please feel free to ask questions in the comments, & I (or other commenters) will try to answer them. Also, I'd welcome any helpful contributions or suggestions.

9:59 PM PT: UPDATE: Definition of "proposition" simplified per suggestion from commenter ends with space.

Extended (Optional)

Originally posted to Brown Thrasher on Wed Apr 04, 2012 at 02:33 PM PDT.

Also republished by Systems Thinking and Logic and Rhetoric at Daily Kos.

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