Online Reading: Fallacies of Evidence - Week #12

INTRODUCTION

During this week, you are fine-tuning your ability to evaluate arguments.  As you practice this week, you'll be focusing on the following question:

1.  What Fallacy of Evidence does this passage commit? 

 

FALLACIES

A fallacy is a mistake in reasoning.  As such, to call an argument fallacious is not to disagree with its conclusion.  Rather, it is to recognize a flawed reason.  It is to note that a premise fails to address the issue at hand. 

There are different types of fallacies.  There are different ways that a premise can fail to address its issue.  During our semester, we will learn about Fallacies of Language, Fallacies of Relevance, and Fallacies of Evidence. 

 

FALLACIES OF EVIDENCE

A fallacy of evidence is a premise that fails to address its issue because it fails to address a burden of proof.    

A claim has a "burden of proof" when there is a need to justify it.  The claim may be true, but it shouldn't be taken for granted.  There is a need for evidence. For example, I may be right to think a student cheated on an exam.  However, if I call the student to my office, and claim that (s)he cheated on the exam, there is a burden of proof.  There is a need to justify that claim. There is a need for evidence. 

A Fallacy of Evidence occurs when one of the argument's claims has a burden of proof, and the issue isn't addressed.

There are many different fallacies of evidence.  During our semester, we will be learning about five of them:

 

APPEAL TO IGNORANCE

An argument commits a fallacious Appeal to Ignorance when a claim is made, the claim has a burden of proof, and the claim is supported by noting that it hasn't been disproven.  For example:  

Of course, my Uncle cheated on his taxes; for he hasn't proven he didn't.  

Maybe this person's uncle did cheat on his taxes.  However, there's a burden of proof.  The claim needs to be justified.  Only, this argument merely points out that it hasn't been disproven.  It hasn't addressed the issue sufficiently. 

 

SLIPPERY SLOPE

An argument relies on a fallacious Slippery Slope when the argument is attempting to justify an action by arguing that acting differently will lead to a negative consequence.  The fallacy is found when this prediction has a burden of proof that it ignored.  The negative consequence is treated as inevitable. Consider the following examples.  First: 

You shouldn't go to bed without studying for the mid-term exam.  For, if you do, you'll fail the class, never graduate from school, and never be able to transfer to a university.

Second: 

You shouldn't go to bed without studying for the mid-term exam.  For, if you do, you'll fail the class. 

Maybe this person shouldn't go to bed without studying for the mid-term.  However, this argument doesn't provide enough evidence.  It assumes it's inevitable that the person will fail the class if (s)he goes to bed without studying for the mid-term.  It treats this as a slippery slope when there is a need to prove this.  It hasn't addressed the issue sufficiently. 

 

FALSE ALTERNATIVE

A False Alternative is an Argument by Elimination that relies on an implausible disjunctive statement.  That is, the disjunctive statement ignores other plausible options. For example:  

Of course, Michael had nothing for breakfast; for he either had eggs or nothing; and he didn't have eggs. 

While Michael may have had nothing for breakfast, this argument merely assumes there are two options: Michael had eggs or Michael had nothing.  There are other options, and they are plausible enough that they need to be addressed.  For example, Michael could have had cereal or pancakes or a smoothie.  In order to prove Michael had nothing, this argument needs to disprove these other options.  Only, the above Argument by Elimination ignores them.  It treats Michael had eggs or Michael had nothing as the only options.  It is a False Alternative. 

 

HASTY GENERALIZATION

A Hasty Generalization is an Inductive Generalization based on a sample that's so insufficient it is hasty.  That is, the argument jumps to a conclusion when there isn't enough evidence to justify one.  Consider the following examples.  First:  

Of course, most students study 20 hours a week; for Linda does.   

Second:  

Of course, most students study 20 hours a week, for most students who get an A in Chemistry do.   

These arguments' samples are hasty. 

The first argument is limited to one student.  Without getting into the details about how many students would need to be sampled (An interesting point worth discussing outside of class), one is not close to enough.  Based on this sample, one shouldn't jump to any generalizations about students. 

Similarly, the second argument is hasty, too.  We don't know how many students were sampled.  But we know it was limited to students who earned an A in Chemistry.  In order to generalize about how many hours most students study, one needs to sample students who get a wider range of grades in a wider range of classes.  Based on this sample one shouldn't jump to any generalizations about students. 

 

QUESTIONABLE CAUSE

A Questionable Cause is a Causal Argument based on evidence that's so insufficient it is hasty.  That is, the argument jumps to a causal conclusion when there isn't enough evidence to justify one.  

Questionable Cause can be a difficult fallacy to recognize.  First, it can be difficult to recognize that the causal conclusion has a burden of proof.  Second, there is no single pattern to look for.  In the end, one has to consider the evidence, and ask if it is hasty.  That said, there is a common example of a Questionable Cause that's worth highlighting.  A Causal Argument attempting to justify its conclusion based solely on a correlation always is hasty.  Correlation is not causation!  A causal conclusion based on a correlation is a prime example of a Questionable Cause.  Consider the following examples.  First: 

Nancy failed the test after going to a movie.  So, it's safe to say she failed the test because she went to a movie.   

Second:  

I just think Bart broke up with Carrie because she got a cat.  For he broke up with her only a week after she got that cat.   

Third: 

I don't care what you think.  My cousin became autistic from a vaccine shot.  After all, he got the shot, and was diagnosed with autism a month later.