Identity, Locke and Objections

Identity can be expressed in a few different formulas.  The reflexivity of identity can be exprssed with "A = A".  In regular language, a thing is the same with itself.  The symmetry of identity is expressed as "If A = B, then B = A".  Meaning that if what you thought were two things are actually identical, then they must be exactly the same in every regard.  The transitivity of identity can be expressed as "If A = B and B = C, then A = C."  In other words, if one thing is identical to two things, then those other two things must also be identical to each other.

A famous objection to Locke comes from a violation of the third expression of identity.  In this blog post, I discuss Thomas Reid's objections to Locke, including the one that is based on a violation of the transitivity of identity.