Critical Thinking: A User’s Manual Chapter 11 Evaluating Causal Arguments

Causal Arguments  A causal argument is an inductive argument that provides evidence that a causal claim is true.  A causal claim is a claim indicating a causal relationship between one event and another.

Causal Claims  Smoking causes cancer.  Having cancer is caused by smoking.  Protests result from political repression.  Protesting is caused by being politically repressed.  The root of sexual violence is pornography.  Being sexually violent is caused by viewing pornography.

Your turn! Restate the following causal claim in the form of one event being caused by another event. Tactical mid-range frequency sonars aboard U.S. Navy ships, that were in use during the sonar exercise, were the most plausible source of the acoustic or impulse trauma to the injured whales.

Gasoline prices have reached their highest level in two years. This must be caused by sabotage of oil fields because extremists have increased their attacks on oil fields in some African countries in the last few months. P1: P2:  Issue:

 Gasoline prices have reached their highest level in two years.  This must be caused by sabotage of oil fields because  extremists have increased their attacks on oil fields in some African countries in the last few months.

Anatomy of Causal Arguments P1: R occurred. P2: P preceded it.  R was caused by P. R = resulting event P = precipitating event M = method of causal reasoning

Mill’s Methods  Method of Agreement: a method of causal reasoning in which the arguer concludes that an event in common among every known instance of the resulting event is the cause of that event.  Method of Difference: a method of causal reasoning in which the arguer concludes that the factor that is different between the occurrence and non- occurrence of the resulting event is the cause of that event.

Three computers in the library’s computer room were corrupted by a new virus. The last user on each computer was the same student, so school officials concluded that he was responsible for the computer damage. P1: P2: R: P: M:

The dam at Lake Isabella has developed some large cracks in the concrete. Since recent seismic activity has occurred on a newly discovered fault in the area, the seismic activity is probably causing the dam to crack. P1: P2:  R: P: M:

Clinical Studies  A clinical study is an inductive argument in which researchers generalize from the results of an experiment (the sample) to a larger population (the target).  The subargument of a clinical study is a causal argument. Researchers conclude that some causal claim is true based on an experiment involving two groups, an experimental group and a control group.

Drinking alcohol can make bike riders more likely to have an accident. A recent study of 40 bike riders showed that the 20 who were given three beers to drink prior to riding the bike performed worse on a riding test than the 20 who did not have the beer. The only difference between the two groups was that one group drank beer and the other did not.

P1: P2:  P:  Issue:

 Drinking alcohol can make bike riders more likely to have an accident.  A recent study of 40 bike riders showed that the 20 who were given three beers to drink prior to riding the bike performed worse on a riding test than the 20 who did not have the beer.  The only difference between the two groups was that one group drank beer and the other did not. 

Evaluating Causal Arguments  Causal arguments may be strong or weak.  Consider how well the arguer demonstrates that the precipitating event is the only reasonable cause of the resulting event.  When there is no evidence that the precipitating event is the only reasonable cause of the resulting event, the argument is a post hoc ergo propter hoc argument.

Which argument is stronger? Three students came to the medical center with acute bacterial ear infections. Since they all went swimming in Thales Pond the day before, getting pond water in their ears must have caused the infection. Three students came to the medical center with acute bacterial ear infections. Since the only thing they had in common is that they all went swimming in Thales Pond the day before, getting pond water in their ears must have caused the infection.

Which argument is stronger? Three students came to the medical center with acute bacterial ear infections. Since the only thing they had in common is that they all went swimming in Thales Pond the day before, getting pond water in their ears must have caused the infection. Three students came to the medical center with acute bacterial ear infections. Since the only thing they had in common is that they all went swimming in Thales Pond the day before, getting pond water in their ears must have caused the infection. None of them had a cold or allergies.

Complete Analysis plus Evaluation Step 1: Write a Basic Analysis of the passage.  Identify the passage.  Analyze the passage. Step 2: If it is an argument, determine whether it commits a fallacy.  Identify the fallacy, and explain how it is committed. Step 3: If it is a nonfallacious argument, diagram it.  Verify that your diagram is consistent with your Basic Analysis.

Complete Analysis plus Evaluation Step 4: Identify the kind of argument.  If the argument is deductive, identify it as a categorical argument or a truth-functional argument.  If the argument is inductive, identify it as an analogical argument, an inductive generalization, or a causal argument.

Complete Analysis plus Evaluation Step 5: Evaluate the argument.  If the argument is categorical, state the syllogism in standard form, and demonstrate whether the argument is valid or invalid using either a Venn diagram or the rules for valid syllogisms.  If the argument is truth-functional, translate the argument, and demonstrate whether the argument is valid or invalid by identifying the argument form, using the truth table method, or using the shortcut method.  If the argument is analogical, evaluate its strength by considering the evidence provided for the analogy and the relevance of the analogy to the feature.  If the argument is an inductive generalization, then evaluate its strength by considering sample randomness and sample size.  If the argument is a causal argument, evaluate its strength by considering the evidence that the precipitating event is the only reasonable cause of the resulting effect.

All of the librarians avoided the flu that was going around this summer. The only preventative step they all had in common was that each had the flu shot given out by the campus clinic. This passage contains an argument. The issue is whether the librarians avoiding the flu was caused by their being given the flu shot. The unstated conclusion is that the librarians avoiding the flu was caused by them being given the flu shot. The first premise is that the librarians avoided the flu that was going around this summer. The second premise is that the only preventive step the librarians had in common was that they each had the flu shot given out by the campus clinic.

 All of the librarians avoided the flu that was going around this summer.  The only preventative step they all had in common was that each had the flu shot given out by the campus clinic.  The librarians avoiding the flu was caused by them being given the flu shot.  +   

This passage contains an argument. The issue is whether the librarians avoiding the flu was caused by them being given the flu shot. The unstated conclusion is that the librarians avoiding the flu was caused by them being given the flu shot. The first premise is that the librarians avoided the flu that was going around this summer. The second premise is that the only preventive step the librarians had in common was that they each had the flu shot given out by the campus clinic. This argument is an inductive causal argument. It is fairly strong because it states that getting the flu shot was the only preventive step the librarians had in common.