What is a logical fallacy

1

• What is a logical fallacy?
• An error in reasoning.
• A breakdown in a logical structure.

2
Fallacies often result from unexamined,
unsupported assumptions.In other words, a
person may assume certain things to be true, to
exist, or to be related and then draw conclusions
based on these assumptions. The conclusion
will be unreliable if the assumptions are faulty.
3

• Harper's new car is bright blue and gets
  excellent gas mileage. Frank's new car is also
  bright blue. Therefore, it probably gets
  excellent gas mileage, too.
• Abuse of the welfare system is rampant nowadays.
  Our only alternative is to abolish the system
  altogether.  
• Immediate steps should be taken to outlaw
  pornography once and for all. The continued
  manufacture and sale of pornographic material
  will almost certainly lead to an increase in
  sex-related crimes such as rape and incest. This
  in turn will gradually erode the moral fabric of
  society and result in an increase in crimes of
  all sorts. Eventually a complete disintegration
  of law and order will occur, leading in the end
  to the total collapse of civilization.  

4

• I just can't face the prospect of living my life
  without the possibility of a heavenly reward.
  Therefore, I know a heavenly reward awaits me at
  death.  
• You should buy Zest toothpaste. Why, 90 percent
  of America brushes with Zest.  
• William Buckley has argued in favor of legalizing
  drugs such as cocaine and heroin. But Buckley is
  just another one of those upper-crust
  intellectuals who is out of touch with real
  America. No sensible person should listen to his
  pseudo-solutions.
• (Child to parent)Your argument that I should
  stop stealing candy from the corner store is no
  good. You told me yourself just a week ago that
  you, too, stole candy when you were a kid.  

5
1.    Faculty and administrators should not be
permitted to come to student council meetings
because student council meetings should be for
students only. 2.    If we can put humans on
the moon, then we should be able to find a cure
for the common cold. 3.    Mary loves good
food therefore, she will be an excellent
chef. 4.    The presiding judge of a
revolutionary tribunal, on being asked why people
were being executed without trial responded with
the following Why should we put them on trial
when we know that theyre guilty? 5.    The
meteorologist was wrong in predicting the amount
of rain for May. Obviously the meteorologist is
unreliable. 
6
6. A doctor can consult books to make a
diagnosis, so a medical student should be able to
consult books when being tested. 7. Because
soft drinks contain so many chemicals, they must
be unsafe. 8. The candidate was poor as a
child, so he will certainly be sympathetic to the
poor if hes elected. 9. Are we going to vote a
pay increase for our teachers or are we going to
allow our schools to deteriorate into substandard
custodial institutions?
7
1. Woody Allen does not deserve a star on the
Hollywood Walk of Fame. He has, after all, been
having an affair with his adopted daughter for
the last three years. This is certainly not the
type of man Hollywood should hold up as an
example.2. Of course the Bible is true. As St.
Paul says, "All scripture is given by inspiration
of God."3. "I'm tired of being called a racist.
I'm not a racist. The racists today are Jesse
Jackson and the NAACP." --Rush Limbaugh.4.
Anti-smoking laws are wrong. If the government
is allowed to ban smokers from smoking in public,
what is to stop them from restricting other
groups of people who do things that other people
don't like, like garlic eaters, gum chewers,
perfume wearers, and whistlers.
8
5. If evolution is true, why has it stopped?6.
I pay for my college education just as I pay for
my groceries at the supermarket with the money I
earn. Why does the administration think it has
the right to tell me what courses I have to take?
Certainly, no one would allow the supermarket to
tell me what groceries I have to buy.7. Miller
Brewing Company has to be the most unscrupulous
American business of the 20th century. I
recently read the story of a Miller employee who,
after 52 years of loyal service, was fired two
days before he would be eligible for full
retirement benefits.8. Need proof that fathers
play an essential role in the development of
young males? Consider this seven of ten men in
jail were raised without fathers.
9
9. Spike Lee is the greatest film director of our
time. No one fills the movie theaters like he
does.10. I hate abortion, but it is better than
a world full of unwanted, abused children and
single mothers killing themselves trying to raise
two or three kids.