Single Idea 17868

[catalogued under 9. Objects / D. Essence of Objects / 4. Essence as Definition]

Full Idea

A surface-functional characterisation is not exhaustive. It allows unintended twins, alien intruders with different structures - water lookalikes that are not H2O and lookalike infinite structures that are not the natural numbers.

Gist of Idea

Surface accounts aren't exhaustive as they always allow unintended twin cases


Joseph Almog (Nature Without Essence [2010], 03)

Book Reference

-: 'Journal of Philosophy' [-], p.366

A Reaction

He rests this on the claim in mathematical logic that fully expressive systems are always non-categorical (having unintended twins). Set theory is not fully categorical, but Peano Arithmetic is. Almog's main anti-essentialist argument.