The Affirming the Disjunct is a type of logical error that occurs when someone mistakenly assumes that one part of a disjunction (an “or” statement) being true means that the entire disjunction must be true. This fallacy gets its name from the fact that affirming one disjunct is not sufficient to prove the truth of the entire disjunction.

Example:

Suppose we have the following statement:

“It’s either raining outside or the sky is blue.”

If someone says, “But it’s definitely raining outside!”, they might think this means the original statement must be true. However, affirming one disjunct (it’s raining) doesn’t necessarily make the entire disjunction true.

Why is this an error?

The Affirming the Disjunct fallacy occurs when someone incorrectly assumes that proving one part of a disjunction automatically proves the entire statement. In reality:

1. One disjunct being true doesn’t guarantee the other’s truth: The two parts of the disjunction are independent, and affirming one doesn’t imply anything about the other.
2. The disjunction itself needs to be evaluated separately: We need to assess whether both parts of the disjunction could be true or false, not just assume that one part being true makes the entire statement true.

Real-world examples:

1. A politician says, “We either need to raise taxes or cut social programs.” If someone responds by saying, “But we definitely need to raise taxes!”,
   they might think this proves the original statement. However, affirming one disjunct (raising taxes) doesn’t necessarily make the entire disjunction true.
2. A doctor tells a patient, “You either have a rare disease or you’re just experiencing normal symptoms.” If the patient says, “But I definitely don’t have the rare disease!”, they might think this means the original statement must be false. However, affirming one disjunct (not having the rare disease) doesn’t necessarily make the entire disjunction false.

How to avoid this fallacy?

1. Evaluate each disjunct separately: Assess whether both parts of the disjunction could be true or false.
2. Consider alternative explanations: Think about possible alternatives that might affect the truth of the entire statement.
3. Don’t assume one disjunct proves the other: Be cautious of assuming that proving one part of a disjunction automatically proves the entire statement.

By recognizing and addressing the Affirming the Disjunct fallacy, you can improve your critical thinking skills and avoid being misled by flawed arguments that rely on incomplete or inaccurate reasoning.

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Filed under: Uncategorized - @ September 25, 2024 9:19 pm