Fallacies of Presumption

These are arguments whose conclusion is supported by false or unproved assumptions.

1.       Accident

2.       Complex Question

3.       Petition Principii or Begging the Question

4.       Ad Consequentiam or Appeal to Consequence

5.       Ad Hoc Rescue

6.       Avoiding the Issue

7.       Red Herring

8.       Excluded Middle or Black/White

9.       Selective Attention

10.   Gambler’s

11.   Inconsistency

12.   Slippery Slope

13.   Straw Man

1.       Accident

                It is when we reason with a generalization as if it has no exemption.

Examples:

“People should keep their promises, right? I loaned Dwayne my knife, and he said he’d return it. Now he is refusing to give it back, but I need it right now to slash up my neighbour who disrespected me.”

“The pull of gravity from this object is 23 kg. So it follows that at the top of Mt. Everest, it is still 23 kg.”

2.       Complex Question

You use this fallacy when you frame a question so that some controversial assumption is made by the wording of the question.

Examples:

“Did you use a knife in killing that man?” [Man: “No”] “Aha! So you did kill him!”

“[Reporter's question] Mr. President: Are you going to continue your policy of wasting taxpayer’s money on missile defense?”

3.       Petitio Principii or Begging the Question

Also known as circular reasoning, this type of fallacy argues by drawing out conclusion that is the same with the premise although expressed differently.

Examples:

“We have the freedom of speech because we have the freedom to express our own opinions.”

“Murder is an immoral act because it is wrong.”

4.       Argumentum ad Consequentiam or Appeal to Consequence

It is arguing that a belief is false because it implies something you’d rather not believe.

Examples:

I don’t believe in your DNA test result. He is my son so we must have the same genes. (The father would not believe since it would imply that the child is not his son.)

Jose Rizal cannot have concubines. He is our national hero.

5.       Ad Hoc Rescue

This fallacy is committed when one tries to rescue a belief by denying a contrary evidence or examples that would falsify it.

Examples:

“If you take Vitamin C every day, you will never get a cold.” [Friend: “But I tried it last year for several months and I still got a cold.”] “Well, I’ll bet you bought some bad tablets.”

“Filipinos are hospitable. If you met a Filipino who is not hospitable, then he is not a true Filipino.”

6.       Avoiding the Issue

It is when one who is supposed to address an issue changed the topic that is not relevant to the issue under consideration assuming that by doing so one can easily dismiss the issue that has to be addressed.

Examples:

When a person is being asked about the status of his marriage but then answered by talking about the schooling of his children, the status of his job, and his relationship to his parents.

“My wife is not a criminal. You see, she’s a good gardener and she loves nature.”

7.       Excluded Middle or Black/White

                You commit this fallacy when you unfairly limit someone to only two choices.

Examples:

“Well, it’s time for a decision. Will you contribute $10 to our environmental fund, or are you on the side of environmental destruction?”

“Either you join our group or you are against us.”

8.       Selective Attention

It is the tendency to look only for evidence in favor of one’s controversial hypothesis and not to look for disconfirming evidence, or to pay insufficient attention to it.

Example:

She loves me, and there are so many ways that she has shown it. When we signed the divorce papers in her lawyer’s office, she wore my favorite color. When she slapped me at the bar and called me a “handsome pig,” she used the word “handsome” when she didn’t have to. When I called her and she said never to call her again, she first asked me how I was doing and whether my life had changed. When I suggested that we should have children in order to keep our marriage together, she laughed. If she can laugh with me, if she wants to know how I am doing and whether my life has changed, and if she calls me “handsome” and wears my favorite color on special occasions, then I know she really loves me.

9.       Gambler’s

Gambler’s fallacy occurs when the gambler falsely assumes that the history of outcomes will affect future outcomes.

Examples:

“I know this is a fair coin, but it has come up heads five times in a row now, so tails is due on the next toss.”

“There was no raid for three months now. So, it’s probably unsafe to continue our drug production next month since there would probably be raid.”

10.   Inconsistency

This fallacy occurs when we accept an inconsistent set of claims, that is, when we accept a claim that logically conflicts with other claims we hold.

Examples:

“I’m not racist. Some of my best friends are white. But I just don’t think that white women love their babies as much as our women do.”

“I agree that everything has a price. But I believe that life is priceless.”

11.   Slippery Slope

This fallacy occurs when one claims that a certain action will lead to an event or chain of events which we do not want.

Examples:

“Do you drink coffee? I am pretty sure that caffeine will not be strong enough, then you will take something stronger, maybe a diet pill. Then, something even stronger. Eventually, you will be doing cocaine. Then you will be a crack addict! So don’t drink that coffee.”

“If we let homosexuals marry each other, then sooner or later, we would also allow people to marry their pets.”

12.   Straw Man

Your reasoning contains the straw man fallacy whenever you attribute an easily refuted position to your opponent, one that the opponent wouldn’t endorse, and then proceed to attack the easily refuted position (the straw man) believing you have undermined the opponent’s actual position.

Examples:

You claim that we must allow same-sex marriage. Therefore, you also claim that marriage is never sacred. If that is your claim, then why should partners (even same-sex partners) be married at all? [The straw man here is you claim that the opponents said that marriage is not sacred even though they did not].

Ladies and gentlemen of the jury, our worthy opponents here believes that capital punishment or death sentence will not help decrease the number of crime incidents in this country. And for that claim they have led themselves into a dangerous pit hole: the belief that every form of punishment is ineffective. As we all know, that is a mistaken belief. Hence, we won this case. [Straw man: your claim that the opponents believe that every form of punishment in ineffective].