The intensional fallacy is a mistake in argument when Leibniz's law is appealed to in an inference involving what Churchland calls "bogus" properties, or an "intensional context."

Examples of intensional contexts:

• John believes that p.
• A is recognizable.
• W is well known.

(This is different from the "intentional fallacy" (with a "t" instead of an "s") discussed in philosophy of art.)

Here's an example of the intensional fallacy:

	Richard Lee is known by all students in this room to have read Descartes' Meditations.
	The elder brother of Margaret Yu is not known by all students in this room to have read Descartes' Meditations.
Therefore,	Richard Lee is not the elder brother of Margaret Yu.

See also Churchland's Muhammad Ali and Aspirin cases at P p. 258b.