Denying a Conjunct

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Contents 1 Synonyms 2 Explanation 2.1 Example 3 Demarcation 4 Category 5 Twin Fallacy 6 External Links 7 Examples in creationist arguments

Synonyms

• Denial of a Conjunct
• Disjunctive Syllogism

Explanation

You commit this fallacy if you interpret the negation of a conjunction (e.g. "not both A and B") as implying at at least one conjunct (either A or B) must be true.

1. Not (A and B)
2. Not A
3. Therefore, B

In order words, confusing a contradiction (where one or the other must be true, but not both) with a contrary (where both could be false, but both cannot be true).

Example

1. Evolution and creationism can't both be true.
2. Evolution is not true.
3. Therefore, creationism is true.

The above example is fallacious as it is possible for both creationism and evolution to be untrue.

Demarcation

You do not make this fallacy if you have good reason for thinking at least one of the conjuncts is true. That is, if the premise "either A or B" is true. Adding this premise without a good reason to do so is known as a False Dichotomy.

Category

• Fallacy of Propositional Logic

Twin Fallacy

• Affirming a Disjunct

External Links

• Fallacy Files [1]

Examples in creationist arguments

• Problems with evolution are evidence for creation

See also examples under the similar fallacy of False Dichotomy.