Affirmative Conclusion From a Negative Premise

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

Synonyms

• Drawing an Affirmative Conclusion from a Negative Premise
• Fallacy of Drawing an Affirmative Conclusion From a Negative Premise

Explanation

This fallacy is committed when a categorical syllogism (i.e. two premises about three categories) has an affirmative conclusion, but a negative premise. This is incorrect because given at least one negative premise, the conclusion must be negative.

For example:

All birds are reptiles, and humans aren't birds, therefore humans are reptiles.

This is invalid because it breaks syllogistic logic: that's why it doesn't even make sense. The exclusion of 'humans' from the 'birds' category gives no reason to include humans in the 'reptile' category. It is easily proven false by finding an example that disproves the conclusion, but doesn't invalidate the premises, such as finding a human that isn't a reptile.

Demarcation

You do not commit this fallacy if you:

• Use two negative premises to draw an affirmative conclusion. That is the fallacy of Exclusive Premises.

Category

• Syllogistic Fallacy

Twin Fallacy

• Negative Conclusion from Affirmative Premises

External Links

• Fallacy Files [1]
• Stephen Downes [2]

Examples in creationist arguments