more from J Baggini / PS Fosl

Single Idea 4640

[catalogued under 9. Objects / F. Identity among Objects / 3. Relative Identity]

Full Idea

The Masked Man fallacy is when Leibniz's Law is taken as 'X and Y are identical if what is true of X is true of Y' (rather than being about properties). Then 'I know X' but 'I don't know Y' (e.g. my friend wearing a mask) would make X and Y non-identical.

Gist of Idea

If identity is based on 'true of X' instead of 'property of X' we get the Masked Man fallacy ('I know X but not Y')


report of J Baggini / PS Fosl (The Philosopher's Toolkit [2003], 3.17) by PG - Db (ideas)

Book Reference

Baggini,J and Fosl,P.S.: 'The Philosopher's Toolkit' [Blackwells 2003], p.103

A Reaction

As the book goes on to explain, Descartes is guilty of this when arguing that I necessarily know my mind but not my body, so they are different. Seems to me that Kripke falls into the same trap.