Logic-Fallacies and Inductive and Deductive Reasoning

Weak Analogy

A comparison between two things that do not relate to each other

Begging the Question

A complicated fallacy, an argument that begs the question asks the reader to simply accept the conclusion without providing real evidence

Circular Reasoning

A type of reasoning in which the premises are recycled in the conclusion creating a circle in reasoning where no useful information is being shared.

In support of her argument that global warming is damaging the environment, Susan cites Al Gore's movie An Inconvenient Truth. However, Gore was a terrible Vice President and his hair looks greasy.

Ad Hominem

There can be no denying that global warming is damaging our ecosystem. Many well-known celebrities and public figures have said so publicly, including former Vice President Al Gore.

Appeal to Authority

People have been trying for centuries to prove that God exists. But no one has yet been able to prove it. Therefore, God doesn't exist.

Appeal to Ignorance

I know my exam is graded based on performance, but you should give my an A. My cat has been sick, and my car broke down, so it was really hard for me to study!

Appeal to Pity

It's perfectly acceptable for the government to treat Native Americans as second-class citizens. After all, the government has treated Native Americans poorly since 1776.

Appeal to Tradition

Post Hoc

Assuming that because B comes after A, A caused B.

Millions have already ordered the new I-phone X. You don't want to miss out on the best phone on the market, so get yours today.

Bandwagon/Ad populum

We know that God exists because we can see the perfect order of creation, an order which demonstrates supernatural intelligence in its design.

Begging the Question

All people have a right to freedom of speech because people should be able to say what they want to say.

Circular reasoning

No triangle is a square because all triangles have three sides and squares hav four sides

Deductive

Sandy was either present or she knew someone who was present. If she was present, then she knows more than she was admitting. If she knew someone who was present, then she knows more than she's admitting. Either way, Sandy knows more than she's admitting.

Deductive

The chances of rolling a five with a die are one in six.

Deductive

This argument is valid because its premises logically entail its conclusion, and any argument whose premises logically entail its conclusion is valid

Deductive

Giving money to charity is the right thing to do. So charities have a right to our money.

Equivocation

The United States had no choice but to invade Iraq. Saddam Hussein had the opportunity to show that he had no weapons of mass destruction, but he failed.

False Dichotomy

My roommate said her philosophy class was difficult and the one I'm in is difficult too. All philosophy classes must be hard

Hasty generalization

Every class I've taken so far has had an even male-female distribution in it. It's obvious, then, that the student population of this college is evenly divided between males and females.

Inductive

If the president stands for re-election, he'll surely be elected. Anyone who thinks the president won't run again just doesn't understand politics or political ambition. So, it's clear who the next president will be, the present incumbent.

Inductive

Since more than half of all automobile accidents involve drivers under 25, it follows that drivers under 25 are probably a greater driving risk than those over 25.

Inductive

Smith missed work today. He must be ill because in the past he's only missed work when he's ill.

Inductive

The chances that there are atmospheric conditions similar to earth's elsewhere in the universe are very high. So, extra-terrestrial life probably exists.

Inductive

The presidential candidate that Maine selects usually indicates the one who'll be elected. So, it's safe to say, "As Maine goes, so goes the nation."

Inductive

The use of statistics indicates which type of argument?

Inductive

Hasty Generalization

Making assumptions about a whole group or range of cases based on a sample that is inadequate

All men are mortal. Socrates is a man. Therefore, Socrates has yellow hair.

Missing the point

Red Herring

Partway through an argument, the arguer goes off on a tangent, raising a side issue that distracts the audience from what's really at stake. Often, the arguer never returns to the original issue.

I hope I presented my argument clearly. Now, my opponent will attempt to refute my argument by his own fallacious, incoherent, illogical version of history.

Poisoning the Well

In 2007, carbon emissions grew globally by approximately 8.8%. The following year, cancer diagnoses increased at approximately the same rate. This indicates that carbon emissions cause cancer.

Post Hoc

Nine months after George Bush took office January 2001, the economy took a nosedive. Thousands of jobs were lost and the stock market dropped by more than 30%. This demonstrates that Bush was a poor economic leader.

Post Hoc

Words the tend to mark an argument as Inductive

Probably, likely, possibly, and resonably

Grading this exam on a curve would be the most fair thing to do. After all, classes go more smoothly when the students and the professor are getting along well.

Red Herring

If we allow homosexuals to get married, who knows what will come next? Soon, people will say they should be allowed to marry multiple people, or even marry animals. It would cause a total societal catastrophe.

Slippery Slope

Enviromentalists think global warming is so serious that we should stop burning all fossil fuels immediately, but doing so would crash the economy and leave millions to starve to death. The solutions to global warming are unfeasible.

Slippery Slope or Appeal to Fear

Jane thinks uniforms are great for identifying students and their schools, but I think uniforms are too costly and parents can hardly afford them, so we should not wear uniforms.

Straw Man

Straw Man

The arguer sets up a wimpy version of the opponent's position to make it easier to knock down

False Dichotomy

The arguer sets up the situation so it looks like there are only two choices. The arguer then eliminates one of the choices, so it seems that we are left with only one option: the one the arguer wanted us to pick in the first place.

Missing the point

The premises of an argument do support a particular conclusion—but not the conclusion that the arguer actually draws.

Guns are like hammers because both have metal parts, and both can be used either as a tool or for harming other people. It would be absurd to restrict the sale of hammers, so it's also absurd to restrict the sale of guns.

Weak Analogy

Appeal to Tradition

a type of logical fallacy in which something is accepted as true or better because it's the way it's always been done

deductive argument

an argument in which it is impossible for the premises to be true but the conclusion be false. It is supposed to be a definitive proof of the truth of the claim (conclusion).

Inductive argument

an argument in which the premises are supposed to support the conclusion. If the premises are true, it is unlikely that the conclusion is false. The conclusion probably follows from the premise.

Appeal to Authority

bolstering/supporting an argument with an unqualified source of authority

Fallacies

defects that weaken arguments

Poisoning the Well

priming the audience with adverse information about your opponent from the start in an attempt to make your claim more acceptable or discount the credibility of your opponent's claim

Appeal to Pity

takes place when an arguer tries to get people to accept a conclusion by making them feel sorry for someone.

Appeal to Ignorance

the arguer basically says, "Look, there's no conclusive evidence on the issue at hand. Therefore, you should accept my conclusion on this issue."

Bandwagon/Ad Populum

the arguer claims that an idea should be accepted because a large number of people believe it to be true. The idea that if X is popular, then X must be true

Ad Hominem

the argument is attacking the person rather than on the argument itself

Inductive reasoning

the process of going from observations to conclusions. This type of conclusion is sometimes called an inference. Inductive Reasoning observes that something is true many times, then conclude that it will be true in all instances. Inductive Reasoning uses the data to make a prediction.

Deductive Reasoning

the process of reasoning from known facts to conclusions. When you reason deductively, you can say, "therefore" with certainty. If your facts were firm to begin with, your conclusions will also be firm.

Equivocation

the sliding between two or more different meanings of a single word or phrase that is important to the argument

Slippery Slope

when a first event is suggested to lead to another event and so on

Appeal to Fear

when someone uses fear to convince another to accept his/her point of view