Logical Fallacies

generalizing from inadequate evidence; stereotyping is (insert logical fallacy here) using prejudiced claims about a group of people

Ezra does not have cancer. She drinks orange juice everyday. Hey! Orange juice must prevent cancer!

using a comparison in which the differences outweigh the similarities or in which the similarities are irrelevant to the claim the analogy is intended to support

Old Joe Smith would never make a good president because an old dog cannot learn new tricks.

Humans are not dogs, and learning the role of president is hardly comparable to learning animal tricks.

using a kind of circular reasoning that offers as proof of an argument a version of the argument itself or using a (presumably) shared assumption to stand for proof

Wrestling is dangerous because it is unsafe.

Unsafe conveys the same idea as dangerous; it does not provide evidence to support the claim that wrestling is dangerous - it merely states that something is something because it is what it is.

non sequitir; reaching a conclusion that does not follow from the premises

Jane Jones is a forceful speaker, so she will make a good major.

It does not follow that speaking ability is an indicator that a person would do well as a major.

post hoc, ergo post hoc; assuming that because two events are related in time, the first caused the second

A new satellite was launched this week, and it has been raining ever since.

This implies, illogically, that the rain (second event) is a result of the satellite launch (the first event)

using two premises that cannot both be true

Only when nuclear weapons have destroyed us all will we be convinced of the need to control them.

This statement is (insert logical fallacy here) in that one one would be around to be convinced if everyone had been destroyed.

ignoring the question; sidetracking the issue by raising a second, unrelated issue

Why worry about pandas becoming extinct when we should be more concerned about the plight of the homeless?

Someone who introduces an irrelevant issue hopes to distract the audience as a (insert logical fallacy here) might distract bloodhounds from a scent.

ad hominem attack; attacking the person making the argument rather than the argument itself

We could take her position on child abuse more seriously if she were not so nasty to the children next door to her.

ad hominem; attacking a person's ideas because of that person's interests or associates

Jack is part of the IGBA, who bankrupted last month, therefore he is unfit to be major.

implying that something is right because "everyone does it"

Hey! Everyone! This popular celebrity eats aloe vera cereal! We should eat it too!

ad verecundium; citing the opinion of a person who has no expertise about the subject

My math teacher said that loreal is the most effective conditioner for all hair types.

ignoring the evidence on the other side of the question

This is the right thing to vote for because (something good and supportive), (something good and supportive), (something good and supportive), etc...

offering only two alternatives when more exist

You better eat your dinner or starve!

separates an idea or a fact from the material surrounding it, thus distorting it for special purposes.

• tabloids
• rumors

assuming that an argument is valid because it has not been proven false

Since no one proved that depression does not cause cancer, let's say that it does.

using expressions that are not clear because they have more than one meaning

• Is she doing well in school?
• She is performing as anticipated.