Invalid Categorical Syllogism (EIO)
An invalid categorical syllogism where the conclusion does not follow: from 'No police dogs are old' and 'Some highly trained dogs are old', it incorrectly concludes that some highly trained dogs are police dogs.
THE IDEA
Invalid Categorical Syllogism (EIO)
From 'No police dogs are old' and 'Some highly trained dogs are old', it does not follow that some highly trained dogs are police dogs. All highly trained dogs could be old and none could be police dogs. That would satisfy both premises while making the conclusion false.
ARGUMENT 1
Premise 1: No police dogs are old.
Premise 2: Some highly trained dogs are old.
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Conclusion: Some highly trained dogs are police dogs.
When to use it
Identifying invalid reasoning in debates and arguments
Teaching logic and critical thinking
Analyzing syllogistic fallacies in everyday reasoning
FROM THEORY TO EVERYDAY LIFE
In practice
The Police Dog Fallacy
Premise 1: No police dogs are old. Premise 2: Some highly trained dogs are old. Conclusion: Some highly trained dogs are police dogs. This is invalid because the premises do not logically entail the conclusion.
A MOMENT TO REFLECT
Put it to work.
Why does the conclusion not follow from the premises?
Can you think of a counterexample that satisfies the premises but makes the conclusion false?
What would a valid categorical syllogism with similar premises look like?
CONTINUE THE CONVERSATION
Source texts
- Mindware Tools for Smart Thinking (Richard E. Nisbett)