Critical Thinking by Example

Fallacy of False Dilemma This fallacy is present when a premise fails to mention all the relevant alternatives. In example 8.2 the author conveniently neglects the alternative that he or she may be the guilty party.
Example 8.2 “Detective Colombo: here is what happened. Only five of us were on the island: me, the victim, Andy, Betty and Charlie. So, the guilty party must be Andy, Betty or Charlie.”
Fallacy of Equivocation This fallacy is present when an argument appears successful only because of an ambiguous premise. In example 8.3, the premise only appears to adequately support the conclusion because of the ambiguity of the word ‘bank’. In one sense it may refer to a type of financial institution, in another sense it refers to the land adjacent to rivers. Presumably the radio report refers to the latter sense of the term, and the conclusion about wet money to the former sense of the term.	Example 8.3 “I heard on the radio that the rains have swelled the river so much that the banks have been flooded. So, your money in the bank must be soaked.”
Fallacy of Vagueness This fallacy is present when an argument appears successful because of the vagueness of the premise set. In example 8.4, the term ‘bald’ is vague. It can mean anything from some loss of hair, to having no hair on one’s head. Since the premise is not more precise, it does not tell us whether the actors have some or no hair, we can’t adequately assess whether the premise supports the conclusion.	Example 8.4 “The intern said that all the actors auditioning are bald. So, we won’t need to worry about how their hair looks, since they have none.”