Following are the main learning objectives from the chapter.
Fallacies of Insufficient Evidence
You should understand that a fallacy of insufficient evidence occurs when an arguer fails to provide sufficient evidence for the conclusion. You should also understand and be able to identify the following fallacies of relevance:
Inappropriate Appeal to Authority: This fallacy occurs when an arguer cites an authority who, there is good reason to believe, is unreliable. You should recognize the following instances of inappropriate appeals to authority:
When the source cited is not a genuine authority on the subject under consideration.
When there is reason to believe that the source is biased.
When the accuracy of the source's observations is questionable.
When the source cited (e.g. a media source, reference work, or Internet source) is known to be generally unreliable.
When the source has not been cited correctly or the cited claim has been taken out of context.
When the source's claim conflicts with expert consensus.
When the claim under consideration cannot be resolved by expert opinion.
When the claim is highly improbable on its face.
Appeal to Ignorance: This fallacy occurs when an arguer appeals to a lack of evidence against some claim as positive evidence that the claim is true, or when an arguer appeals to a lack of evidence for some claim as positive evidence that the claim is false.
You should understand the specific exceptions to the rule on appeals to ignorance:
When a careful search that would likely have found evidence if there was evidence to be found has failed to do so.
When special rules require that a claim be rejected as false until a certain burden of proof has been met.
False Alternatives: This fallacy is committed when an arguer poses a false dichotomy.
Loaded Question: This fallacy is committed when an arguer asks a question that contains an unwarranted assumption.
Questionable Cause: This fallacy occurs when an arguer gives insufficient evidence for a claim that one thing is the cause of another. You should recognize the following instances of Questionable Cause:
Post hoc fallacy: This fallacy occurs when an arguer assumes, without adequate reason, that because one event precedes another, that the first event was the cause of the second.
Mere correlation fallacy: This fallacy occurs when an arguer assumes, without adequate reason, that because two conditions or events regularly occur together, that there must be a causal relationship between them.
Oversimplified cause fallacy: This fallacy occurs when an arguer assumes, without sufficient evidence, that a single condition or event is the sole cause of some effect, when there are in fact other contributing causes.
Hasty Generalization: This fallacy occurs when an arguer draws a general conclusion from a sample that is either biased or too small.
A biased sample is one that is not representative of the target population.
The target population is the group of people or things that the generalization is about.
Hasty generalizations can often lead to false stereotypes.
Slippery Slope: An arguer commits this fallacy when they claim, without sufficient reason, that a seemingly harmless action will lead to a disastrous outcome. Slippery slope arguments generally follow this pattern:
The arguer claims that if a certain seemingly harmless action, A, is permitted, A will lead to B, B will lead to C, and so on to D.
The arguer holds that D is a terrible thing and therefore should not be permitted.
In fact, there is no good reason to believe that A will actually lead to D.
Weak Analogy: When the conclusion of an argument depends upon a comparison between two (or more) things that are not similar in relevant respects, the fallacy of weak analogy is committed. This fallacy generally follows the pattern:
A has characteristics w, x, y, and z.
B has characteristics w, x, and y.
Therefore, B probably has characteristic z, too.
But characteristics w, x, and y are not relevant to z or,
A and B have differences relevant to z which are ignored by the arguer.
Inconsistency: This fallacy occurs when an arguer asserts inconsistent premises, asserts a premise that is inconsistent with his or her conclusion, or argues for inconsistent conclusions.