Logic 15-- Lesson 32, Making a Standard Argument.
To make a valid syllogism in an argument:
1. Write the desired conclusion in categorical form.
2. Find a valid syllogism (mood/figure) (see pg 201)
3. Fill in the major term and minor term in the major/minor hypotheses, leaving blanks for the middle
term.
4. Find an appropriate middle term to fill in, so that the hypotheses are undeniably true.
All men are idolaters.
There are Christians who are rich.
No man can serve two masters.
Again, be careful:
Show that ‘all men go to heaven’
By the following valid AAA-1 syllogism
All persons loved by God are goers-to-heaven.
All men are persons loved by God.
All men are goers-to-heaven.
The syllogism is valid, but the argument is not ___________________________.
Lesson 33 Fallacies of Distraction
An informal fallacy is an argument whose stated premises fail to support their proposed conclusion.
These fallacies usually involve errors in language/communication rather than in logic.
*** I disagree greatly with our author in this section *****
1. Ipse dixit (appeal to an authority, usually self authority)
Erie is not a nice city, because I said so.
Miss. Manners says that burping in public is unacceptable, so it must be unacceptable.
Sometimes, an appeal to authority is good, but technically not part of an argument relying soley
on logic.
The Bible says Christ rose from the dead. So He must have. (This would be accepted by a Bible
believing Christian, but rejected by an atheist.)
2. Ad populum (appeal to the masses) (related to ipse dixit, where the majority becomes the authority)
Most people think Sunday is the new Sabbath Day, so it must be so.
Most people think a man and woman living together outside of marriage is acceptable. So it
must be so.
Most people think the world will not end in 2012, so it won’t.
3. Ad baculum (appeal to force)
If you don’t stop eating Twinkies, you will die young.
If you don’t believe in God, you are going to hell.
If you don’t believe Allah is God, we will kill you.
4. Ad hominem (attack of the arguer rather than their argument)
Your claims are unbelievable, since you are a liar.
Your claims are unbelievable, since you have been convicted 9 times of perjury.
Again, ad hominem may actually carry weight (the person may indeed be a liar and this should
be taken into account), but the person’s argument should itself be able to be analyzed for its logical
soundness independent of the person’s character.
5. Bulverism (arguing against a position by arguing against how someone came to hold it)
Surely all animals are not clean to eat, since you were told that in a dream.
You just believe in Christ because you were raised a Christian.
6. Tu quoque (you do it so I can) inconsistency between argument and arguers behavior.
How can you tell me that being angry is wrong, you do it all the time!
Since you healed on the Sabbath, you must think the Sabbath is like any other day.
7. Ad Ignorantiam (argument from lack of facts)
Santa Claus must exist, since no one can conclusively prove he doesn’t.
I am innocent until proven guilty.
8. Chronological snobbery
The Puritans taught that homosexuality was bad, but we know better now.
They used to think leeches cured people, but we know better now. (the reason for leeches
working/not working has nothing to do with what they thought of tem in the past).
Accupuncture is ancient medicine and so it has no place in any modern treatments.