“Some humans are teachers” and “Some teachers are human” are legitimate particular-affirmative converses. But “Some humans are not teachers” does not entail “Some teachers are not human.”
The first pair follows the valid conversion of a particular affirmative. A particular negative cannot be converted in this way.
When a fourth-figure table displays a particular negative, its subject and predicate must not be reversed without a separate valid argument.
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The Fourth Figure: Productive Conditions, Moods and Proofs
“Some humans are teachers” and “Some teachers are human” are legitimate particular-affirmative converses. But “Some humans are not teachers” does not entail “Some teachers are not human.”
The first pair follows the valid conversion of a particular affirmative. A particular negative cannot be converted in this way.
When a fourth-figure table displays a particular negative, its subject and predicate must not be reversed without a separate valid argument.