Martha's friend, who is very knowledgeable about edible flowers, told Martha that there are no edible daisies, at least not any that are palatable. ███████ ████████ ███████ ████ █████ █████ ███ ███████ ████ ███ █ ████ ██ █████████████ ███ █████ █████ ███ ██████ ██████████████ ████ ███ █████ ██████████ ████ ███ ██████ ████ ███ ████ ██ ██████████
Martha concludes that there are some daisies that are both edible and palatable. Her reasoning is that some chrysanthemums are edible and palatable, and some chrysanthemums are daisies.
We don’t know if there’s any overlap between the subset of chrysanthemums that are edible and palatable and the subset that are daisies. It’s possible that none of the edible and palatable chrysanthemums are also daisies. Therefore, Martha’s inference is invalid.
Consider an analogous argument: Some people who wear masks are bank robbers, and some people who wear masks are nurses. Therefore, some bank robbers are nurses.
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