Identity: Logic, Ontology, Epistemology
Greece is Hellas and Greeks are Hellenes. Azure is cobalt and everything (coloured) azure is (coloured) cobalt. Pre-Fregeans would call all these statements of identity. Frege taught us to distinguish between
Conaming [Name] [Name]. Ngh: Greece is Hellas g=h. Nac: Azure is cobalt a=c
Copredicating [Predicate] [Predicate]. PGH: Greeks are Hellenes (x)(Gx[identical with]Hx). PAC: Everything azure is cobalt (x)(Ax[identical with]Cx)
Singular Predication [Name] [Predicate]. PcA: Como is azure Ac. PaC: Azure is a colour Ca. PaL: Azure is like indigo Lai. PgD: Greece defeated Persia Dgp.
With Frege the contrasts became marked but misconceived.