Logical Fallacies Practice

What is a logical fallacy?

• A type of reasoning that begins with a general principle and applies it to a single example

• A conclusion in reasoning to which a logical argument leads

• A mistake in reasoning that makes an argument less effective

• A type of reasoning that uses a specific example to create a general rule

Identify the type of fallacy being used:

If you vote against the proposed mall project, then you must be against creating jobs for our community.

• Slippery Slope

• Post hoc

• Either-Or

Answer explanation

Acts as if there are only two options.

Identify the type of fallacy being used:

After Blake listened to the record, he was sad; therefore, it must have been the record that upset him.

• Slippery Slope

• Post hoc

• Either-Or

Answer explanation

Acts as if listening to to music caused him to be sad. Post hoc- A causes B

Identify the type of fallacy being used:

If we pave over Jenkins Park for a parking lot, this will happen again and again until there's no grass left in this town.

• Slippery Slope

• Post hoc

• Either-Or

Answer explanation

It suggests that a single event will inevitably lead to extreme events or situations. Slippery Slope= A leads to B leads to C leads to D....to Z

Which logical fallacy is most prominent in the following passage?

You've just sat here for an hour and listened to my opponent's long-winded, eight-part explanation about how he'll "look to the future" by allotting more of the budget to educational programs. But do you really want someone in office who shifts funding away from crucial areas such as health care and defense? In his future, we'd be sickly and conquered, but we'd sure be smart!

• Bandwagon

• Straw man

• Post hoc

Answer explanation

This passage contains the straw man fallacy, which occurs when someone oversimplifies an opponent's argument or position to make it easier to attack.

Which sentence from the passage contains a flaw in logic?

For a long time, my colleagues at FreeTime Travel have debated over whether Scotland or Ireland is the better vacation destination, though up until this year the two countries have been equally popular. Data from the past year have finally produced a clear answer. Since twice as many people traveled to Scotland than Ireland this year, it's clear that Scotland is the better choice for your next trip. And when you're ready to book that trip, come see us here at FreeTime Travel.

• For a long time, my colleagues at FreeTime Travel have debated over whether Scotland or Ireland is the better vacation destination, though up until this year the two countries have been equally popular.

• Data from the past year have finally produced a clear answer.

• Since twice as many people traveled to Scotland than Ireland this year, it's clear that Scotland is the better choice for your next trip.

Answer explanation

This section of text argues that because a large number of people think or act a certain way, others should too. Therefore, it's an example of a bandwagon fallacy.

Which best analyzes how the post hoc fallacy weakens the argument in this passage?

In order to draw more residents to Arlington, we need look no further than the Riverwalk Parkway. In the year after the parkway was built in 2005, the population of Arlington has risen by 20 percent, nearly triple the growth of any other year. Clearly people value their recreational space and will even relocate to get it. Therefore, we should double the length of the Riverwalk Parkway in order to light the fuse for another population boom.

• It suggests the author does not really understand the opposing argument or is choosing to distort it to strengthen his or her own claim.

• It suggests the author believes that because one event occurred before another, the first event must have caused the second.

• It suggests the author believes that a single example will inevitably lead to extreme events or situations.

• It suggests the author sees only two possible options for increasing the population of Arlington, when in fact there are many more.

Answer explanation

A post hoc fallacy weakens an argument by mistaking a relationship in time for a cause-and-effect relationship. In this case, building the parkway didn't necessarily have anything to do with the population boom that followed it.

Which best explains how the logical fallacy weakens the author's argument in the following passage?

I recently came across an article in the Journal of Arbor Studies that details how the planting of new trees can drastically improve air quality in communities such as ours. We all know, of course, that due to increased traffic and industrial pollution, the air quality here in Breslow has been steadily deteriorating, and unless we do something it will continue on into the future. Therefore, I urge the city council to pass my proposal to purchase and plant 10,000 new trees across the city. If you fail to pass this proposal, it will be clear you don't care about the health and prosperity of future generations.

• It shows the author has not considered alternative reasons why the council might reject the proposal.

• It shows the author has not done any research to support his or her argument about purchasing and planting trees.

• It shows the author has jumped to conclusions about the negative effects of the proposal on future generations.

• It shows the author is making highly unlikely cause-and-effect connections to explain the poor air quality.

Answer explanation

This either-or argument presents only one perspective: If you don't agree to plant the trees, then you don't care about future generations. There may be other factors at work, however, such as the cost of the trees or available space to plant them.

Identify the logical fallacy in this passage:

I recently spoke to one of the English teachers over at Roosevelt High, who told me she was considering adding a graphic novel — a glorified comic book, I say — to the curriculum next semester. A "critically acclaimed" one, she was sure to note, that would allow the class to discuss "how new genres were reshaping the way we read." Sure, it starts with one graphic novel to teach a lesson. Then it's a series of them, followed by a whole semester's worth, and pretty soon that's all these kids will be reading in school. Goodbye, Shakespeare! — unless it's in comic form, I suppose. And once the classics are no longer taught in high school, you'd better believe they'll disappear from society as a whole.

• I recently spoke to one of the English teachers over at Roosevelt High, who told me she was considering adding a graphic novel — a glorified comic book, I say — to the curriculum next semester.

• A "critically acclaimed" one, she was sure to note, that would allow the class to discuss "how new genres were reshaping the way we read."

• Sure, it starts with one graphic novel to teach a lesson. Then it's a series of them, followed by a whole semester's worth, and pretty soon that's all these kids will be reading in school. Goodbye, Shakespeare! — unless it's in comic form, I suppose. And once the classics are no longer taught in high school, you'd better believe they'll disappear from society as a whole.

Answer explanation

This argument contains the slippery slope fallacy. It suggests that the author believes a single example will inevitably lead to extreme events or situations. In this case, the author is assuming a worst-case scenario instead of thinking or speaking logically about the issue. By quickly jumping to unrealistic and extreme examples

Which statement best analyzes the logic in these sentence from the election speech?

You elected me as your vice president last year, and do you remember how great the past year has been? Our women's soccer team won the state championship, and the new swimming pool opened. If you vote for me, next year will be even better.

• The sentences use the post hoc fallacy; the logic is flawed because the positive events were probably not caused by the candidate's actions.

• The sentences use the straw man fallacy; the logic is flawed because no one is actually claiming that the past year was not great.

• The sentences use the slippery slope fallacy; the logic is flawed because good things that happened last year might not repeat this year.

• The sentences do not use a fallacy; the logic is valid because positive events are a good reason to vote for a candidate who has previously served in student government.