Categorical distinctions in syntax and semantics are drawn on the basis of the distribution of linguistic expressions. According to the classical definitions, two expressions belong to the same syntactic category just in case they can be interchanged in every well-formed context salva beneformatione (without loss of well-formedness) and they belong to the same semantic category just in case they can be interchanged in every meaningful context salva significatione (without loss of meaningfulness) (Bar-Hillel 1953). The question is what counts as interchange in a context. Interpreting this phrase naïvely will result in inadequate definitions: Intuitively, one cannot conclude that "You are bald" and "I am bald" belong to different syntactic categories because "Most people who like you are bald" is well-formed, whereas "Most people who like I am bald" is not. Likewise, it cannot be concluded that cat and dog belong...