Breaking down a symbol

The Greek word symbolon means something put together-originally a coin (or potsherd) broken into 2 pieces, one of which was given to each of the parties in a legal agreement as identification. This half coin became a symbol: it hinted that something more was needed to complete its meaning.

A symbol that has to explain itself, that feels apologetic about its presence, is not a healthy symbol.

The poet who works in symbols is likely to give more care to the vividness of his images than to the abstractions they stand for. Images can sometimes be so real that we are not at first aware they are symbols, though something a little strange about them may lead us to feel perhaps only half consciously, that more is going on than we are aware of. 

-John Frederick Nims, Western Wind: An introduction to Poetry, 1974