Fallacious counterposition of a categorical proposition

A fallacious counterposition occurs when both subject and predicate of a categorical proposition are negated and swapped as if truth were preserved.

Example

“All A are B”
“Therefore, everything that is not B is not A”
(That transformation is not always valid in natural language.)

Applied example (political)

“Some politicians are corrupt; therefore some honest people are not politicians.” (Negation and swap do not follow.)

Applied example (mystical)

“Some rituals are symbolic; therefore some non-symbolic things are not rituals.” (It does not follow from the premise.)

Why it is fallacious

• It changes logical structure without guaranteeing equivalence.
• It mishandles quantifiers.
• It yields conclusions that do not follow from the premise.

How to spot it

• Subject and predicate are inverted after both are negated.
• Subtle shifts between “all” and “some”.
• Formal-looking deductions without proof of validity.

How to respond

• Ask for a logical demonstration of equivalence.
• Test with concrete counterexamples.
• Restate the proposition with clear quantifiers.