Bad Arguments

Generalisations

•Smoking can’t be dangerous – my grandmother smoked 20 cigarettes everyday and died in her sleep when she was 93.

•Australians are friendly

Bad Arguments

Bandwagon fallacy

It’s the most popular therefore it’s the best

• Most people use Microsoft Office.

Circular Argument

•believe in the bible because in the bible it says that God says you must.

Bad Arguments

Wrong correlation

Some P are not Q. Therefore, some Q are not P.

Some dogs are not pets. Therefore, some pets are not dogs.

Bad Arguments

Wrong correlation

Some P are not Q. Therefore, some Q are not P.

Some dogs are not pets. Therefore, some pets are not dogs.

Some mammals are not cats. Therefore, some cats are not mammals.

Bad Arguments

Wrong correlation

Alcoholics generally don’t earn much money

Research shows that children who watch more than 4 hours of TV a day usually have low marks at school

Mermaids exist because no-one has proved they don’t

There is a plot by John Smith to take over the country – look how strongly he denies it

Bad Arguments

Wrong correlation

Event C happened immediately prior to event E. Therefore, C caused E.

•The only policy that effectively reduces public shootings is right-to-carry laws. Allowing citizens to carry concealed handguns reduces violent crime. In the 31 states that have passed right-to-carry laws since the mid-1980s, the number of multiple-victim public shootings and other violent crimes has dropped dramatically. Murders fell by 7.65%, rapes by 5.2%, aggravated assaults by 7%, and robberies by 3%.

Bad Arguments

2 wrongs don’t make a right

•It is completely right to not go back to a store if they give you too much change, because if they didn’t give you enough change, they wouldn’t do anything about it.

Bad Arguments

Surveys

•Is the sample scientifically selected or self- selected? How big is it? Is it broad?

•What is the survey's margin of error? Are any comparisons reported - such as changes in popularity, record highs or lows, or comparisons between candidates.

•Have other surveys on this issue been done recently? If so, compare the new poll with these others. If the results of the new poll are significantly different from those of most other polls, then the new poll is probably unreliable.

Bad Arguments

Inference

1.Joe: Did you eat the chocolate bars on my desk?

Kay: I’m on a diet, I definitely didn’t eat the mars bars.

2.I bought John a Xmas present because I like him more than Fred.

Bad Arguments

Your turn

•With a partner or by yourself choose some arguments from the Worksheet handout and discuss/analyse what is wrong with them.