Why is AAE-2 Invalid?

Mr. Nance,

I am working on the 256 forms of syllogisms right now and I’m confused why one of them is invalid. I’m on the AAE-2 and each way I work it out, it comes out valid. Could you please tell me why it’s invalid.

Thank you!

AAE-2 is invalid in part because the minor term could be a species of the major term. For example, salmon are a species of fish, so this is a counterexample: “All fish are creatures. All salmon are creatures. Therefore, no salmon are fish.” The premises are true, but the conclusion is false, thus the syllogism is invalid. (It also is the fallacy of two affirmative premises and a negative conclusion, but you may not have gotten to the rules of validity yet.)


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