Ambiguity Fallacy
When an unclear phrase or word with multiple definitions is used in an argument, shifting meaning between premises and conclusion, the argument becomes unsupported. This fallacy relies on linguistic ambiguity to mislead.
THE IDEA
Ambiguity Fallacy
(also known as: amphiboly, semantical ambiguity, type-token ambiguity [form of], vagueness)
Description: An argument relies on an unclear phrase whose meaning changes in a way that leaves the conclusion unsupported. Some will say single words count for the ambiguity fallacy, which is really a specific form of a fallacy known as equivocation.
Logical Form: The source provides no general form here.
Example #1: The original argument is missing; only its commentary remains.
Explanation: The ambiguity here is what exactly “good understanding” means. The conclusion assumes a much better understanding than is suggested in the premise, therefore, we have the ambiguity fallacy.
Example #2: The original argument is missing; the commentary describes changes of meaning.
Explanation: This argument is guilty of two cases of ambiguity. First, the first use of the phrase, “come from”, refers to reproduction, whereas the second use refers to origin. The fact that we know quite a bit about reproduction is irrelevant when considering origin. Second, the first use of, “living being”, refers to an empirically verifiable, biological, living organism. The second use of, “living being”, refers to a belief of an immaterial god. As you can see, when a term such as, “living being”, describes a dodo bird as well as the all-powerful master of the universe, it has very little meaning and certainly is not specific enough to draw logical or reasonable conclusions.
Exception: Ambiguous phrases are extremely common in the English language and a necessary part of informal logic and reasoning. Ambiguity alone does not establish a fallacy. The issue is whether the argument depends on incompatible readings of the same expression.
Variation: Type-token ambiguity confuses a category with an individual instance. For example, Prius, RAV4, and Camry name models; an individual vehicle is a token. A count of models and a count of manufactured vehicles answer different questions. The source’s original counting statement is missing.
When to use it
Analyzing advertising slogans that rely on double meanings to imply benefits without evidence.
Evaluating political speeches that use vague terms like 'freedom' or 'reform' to appeal to diverse audiences.
Clarifying instructions or contracts where ambiguous wording could lead to different interpretations.
FROM THEORY TO EVERYDAY LIFE
In practice
Good Understanding
Ambiguity in the phrase 'good understanding' – premise suggests a basic grasp, but conclusion assumes deep comprehension.
Origin of Living Beings
Two ambiguities: (1) 'come from' shifts from biological reproduction to metaphysical origin; (2) 'living being' shifts from empirical organism to immaterial deity.
A MOMENT TO REFLECT
Put it to work.
Can you identify an ambiguous phrase in a recent argument? How did shifting its meaning affect the conclusion?
How can you ensure your own arguments avoid ambiguity by defining key terms?
Why is it important to distinguish between different meanings of a word in logical reasoning?
CONTINUE THE CONVERSATION
Source texts
- Logically Fallacious - The Ultimate Collection of Over 300 Logical Fallacies