Naming theory (Plato)命名论Words are names or labels for things. 词语只是代表物体的名字或标记。
Limitations: 1) Applicable to nouns only. 2) There are nouns which denote things that do not exist in the real world, e.g. ghost, dragon, unicorn, phenix… 3) There are nouns that do not refer to physical objects but abstract notions, e.g. joy, impulse, hatred…