Review Part 2

Critical Thinking

Is there any evidence to support the claim?

Is the evidence reliable and trustworthy? How reliable is it? Should you accept it?

Does the evidence actually support the claim?

Is there other evidence you should consider?

Popularity, Tradition, Ignorance

Fallacies:• Appeal to popularity: arguing that something

is true because it’s popular.• Appeal to tradition: arguing that something is

true because it’s traditional.• Argument from ignorance: arguing that

something is true because it hasn’t been proven false.

Not Fallacies

The following things are not fallacies:

• Having traditions• Being popular• Lacking evidence

Appeal to Popularity

After Fukushima, many people in China and California rushed out to buy salt.Why? Some people may have had some dumb scientific idea, but for most it was because that’s what everyone else was doing.

Antonin Scalia

• Longest serving justice on US Supreme Court.

• Taught at the University of Chicago.

• First Italian-American SC justice.

• Extremely powerful and influential

Interview with Scalia

Q: Isn’t it terribly frightening to believe in the Devil?

Scalia: You’re looking at me as though I’m weird. My God!... Most of mankind has believed in the Devil, for all of history. Many more intelligent people than you or me have believed in the Devil.

Appeal to Tradition

“With a history of more than 2000 years, Traditional Chinese Medicine (TCM) has formed a unique system to diagnose and cure illness.” – eastday.com

Argument from Ignorance

“Absence of evidence is not evidence of absence.” – Carl Sagan

Just because there is no evidence that something is true, does not mean that it is false.

Just because there is no evidence that something is false, does not mean that it is true.

Shifting the Burden of Proof

A similar fallacy is “shifting the burden of proof”. It goes:

“God exists. If you think otherwise, prove that he doesn’t!”

Here, you make a claim (“God exists”) but instead of giving evidence for it, you require that your opponent give evidence for the opposite.

Appeal to Authority

It’s OK to find out what to believe from experts in many cases. However, this is not true when:• The expert is not an expert about what you

want to know.• Experts in general disagree about the

question.• The expert has a history of lying or misleading

about the question.

Irrelevant Evidence

There are many ways that evidence can seem to support a conclusion, without actually doing so:

• No connection with the claim.• Circular reasoning.• Better alternative explanations.• Special circumstances.

No Connection with the Claim

• Clustering illusion: it looked like there was a pattern there, but there wasn’t.

• Regression fallacy: going back to normal seemed to be for a reason, when it wasn’t.

• Base rate neglect fallacy: a reliable test said the claim was true, but since the base rate of the condition is very low, it is still unlikely that the claim is true.

Circular Reasoning

Circular reasoning involves trying to show that a claim is true by assuming that it is true in the premises. It has the form:

X is true. Why? Because X.

Carbon Dating

The Earth’s atmosphere contains a mix of carbon, including regular carbon (C-12) and also radioactive carbon, C-14.

Plants take in carbon for photosynthesis, trapping both types of carbon. Animals eat the plants and trap the carbon too.

Carbon Dating

Once an organism dies, it stops trapping carbon.

C-14 decays at a constant rate into nitrogen-14. So the ratio of carbon-12 to carbon-14 slowly goes up over time in a dead organism.

We can use this ratio to determine how old something is!

Circular?

Some young-Earth creationists argue that carbon dating is circular.

Scientists say this bone is 50,000 years old because carbon dating says so. But how do we know that carbon dating is correct? Because this bone is 50,000 years old, and you can see that carbon dating gets the right answer!

Straw Man Fallacy

A straw man argument is where you mischaracterize your opponent’s claims or reasons for those claims. You show that the mischaracterization is false or misleading, and then claim that your opponent believes false claims or has bad reasons for her claims.

Straw Man Fallacy

Many in Hong Kong think that President Benigno Aquino of the Philippines should apologize for the Manila bus crisis.

People feel so strongly they have been heartless after the recent tragedy.

Straw Man

Aquino argues:1. No one should apologize for something that

they did not do. 2. Rolando Mendoza acted alone in taking

hostages and in killing hostages. The Philippine government didn’t do it and the Philippine people didn’t do it.

3. Therefore, the government/ people of the Philippines should not apologize.

Straw Man Fallacy

Aquino is suggesting that people want him to apologize for Mendoza’s actions.

BUT that is not what people want. They want him to apologize for the Philippine government’s actions: specifically, the way the crisis was mishandled by the police.

False Dilemma

An argument commits the false dilemma fallacy when it presents two options as the only options, even though there are actually more options.

National Education

1. We can either have national education with the materials we now have, or not have national education.

2. The materials now falsely portray China and ignore historical events like Tiananmen Square.

National Education

3. Therefore, there should be no national education in Hong Kong.

Fallacy of the Mean

The fallacy of the mean is the assumption that a “middle point” between two views is the right one.

Distribution Fallacy

The distribution fallacy is when you assume that the parts have the same properties as the whole they comprise:

1. Lingnan has a great philosophy department.2. Therefore, Michael is a great philosopher.

1. For the “whole” of Hong Kong kindergartens, there is enough space for all children to go to school.

2. Demand is for 168,000 spaces, but there are a total of 241,000 spaces.

3. Therefore, there is no shortage of space in kindergartens.

Distribution Fallacy

Just because there is enough space in the whole system does not mean there is enough space in the high-demand districts.

Mainlanders want to go to kindergarten in the northern districts, because that’s closer to China. These kindergarten seats have much lower availability.

Ecological Fallacy

The ecological fallacy is a form of the distribution fallacy– a particularly tricky one!

As we saw before, just because Catholic countries have fewer suicides than protestant countries, doesn’t mean that Catholics commit less suicide!

Blue = Democrat

Green = $$$

Ecological Fallacy

States with the highest average incomes have a higher percentage of democratic voters.

So does this mean that people who are wealthy are more likely to vote democrat?

No! The opposite is true.

Appeal to Nature

The appeal to nature fallacy is when someone argues that something is true/ good because it’s natural or when they argue that something is false/ bad because it’s unnatural.

Harmful “Natural” Ingredients

Pure sugar pills (or saltwater injections) can’t harm you any more than your beliefs can (which can be significantly).

But invasive treatments or treatments with pharmacologically active ingredients can harm you, even if they are only as good as a placebo at helping you.

Cancer in Taiwan

Taiwan has the highest per-capita incidence of UUC (upper urinary tract cancer) of anywhere in the world.Plants of the genera Ephedra and Asarum produce the toxic chemical aristolochic acid which causes UUC.TCM herbal remedies contain lots of these plants, and tests have shown they contain aristolochic acid as well.

Kidney Failure in Belgium

In a case report in “Nature” in 2011, a “slimming clinic” in Belgium where women were taking Chinese herbal remedies led to more than 100 women suffering kidney failure and many of them later developing cancer…

From aristolochic acid, the same thing making Taiwan #1 in UUC!

Other Harmful Side-Effects

Here’s a bottle of Saiga Antelope Horn Powder. The Saiga Antelope is critically endangered, so the fact that people take these pills is currently harming endangered species.

Is there other evidence we should consider?

This is what we talked about in the first week: context. But it’s not always true that when we should consider more evidence, something has been taken out of context.

Out of Context

Words are taken out of context when:• You present some, but not all, of what

someone said.• What you present makes it seem as if they

believe or support some claim.• If we look at all of what they said, it is clear

that they do not support or believe that claim.

Out of Context: 1998-present

Broader Context: 1850-present

Are there lots more Americans on Welfare?

…Not really.

The Fallacy Fallacy

This is a bad argument:

1. You have presented argument A for your claim C.

2. A is a fallacious argument.3. Therefore, C is false.

CORRELATION AND CAUSATION

Causation

Much of science is concerned with discovering the causal structure of the world.

We want to understand what causes what so we can predict, explain, and control the events around us.

Causation ≠ Correlation

http://www.critthink2.org/2011/05/23/lisa-simpson-demonstrates-causal-reasoning/

Homer: Not a bear in sight. The Bear Patrol must be working like a charm.

Lisa: That’s specious reasoning, Dad.

Homer: Thank you, dear.

Lisa: By your logic I could claim that this rock keeps tigers away.

Homer: Oh, how does it work?

Lisa: It doesn’t work.

Homer: Uh-huh.

Lisa: It’s just a stupid rock.

Homer: Uh-huh.

Lisa: But I don’t see any tigers around, do you?

Homer: Lisa, I want to buy your rock.

Causation ≠ Correlation

But causation does not imply correlation. If A and B are correlated there are several possibilities:

• A causes B• B causes A• C causes A and C causes B• A and B are only accidentally correlated

B causes A

B causes A

B causes A

B causes A

B causes A

C causes A and B

Much more common than “B causes A” explanations are explanations where the causal relationship between A and B is due to a third variable.

Common Cause!

From the Daily Mail

Lede: “[new] findings, published in the latest online edition of the journal Appetite, show the way we perceive tasty treats like chocolate cake is just as important as the calorie count when it comes to expanding waistlines.”

From the Daily Mail

“They recruited almost 300 volunteers, aged from 18 to 86, and quizzed them on their eating habits and whether they were trying to lose weight. They also asked them if eating chocolate cake made them feel happy or guilty.

The results showed 27 per cent associated it with guilt and 73 per cent with celebration. When the researchers looked at weight control 18 months later, they found those riddled with guilt had gained significantly more.”

Probably Common Cause

Maybe people who eat unhealthily feel more guilty about eating chocolate. After all, they can see the harm they’re doing to themselves.

And maybe people who eat very well don’t feel guilty having chocolate.

Coincidence

In 1979, two researchers, Nancy Wertheimer and Ed Leeper, published an article alleging that the incidence of childhood leukemia was higher in Denver neighborhoods that were near electric power lines.

The “Texas Sharp Shooter”

Suppose I stand in front of a barn. I have a machine gun with me, and I am blindfolded. I shoot wildly at the barn for several minutes.

Afterward, I walk up to the barn. I find a spot where three bullets are very close together, and I paint a target around them. “Look!” I say, “at what an excellent marksman I am!”

Power Lines and Cancer

The power lines study is just like this.

The researchers found places near power lines and looked at all the health problems anyone had in the area.

Of all the health problems what’s the chance that one is accidentally correlated with power lines?

Coincidence

High enough!

Later studies showed there was no relationship.