"The price of metaphor is eternal vigilance."
Metaphor erodes as we are distanced from the cultural and chronological context of the original statement. The Bible is shackled so. This week I read Luke 6 and 7. The Father, The Son of Man, Elijah, Israel, Heaven all lie heavy on the page.
Perhaps erode is the wrong word. The metaphors have been "fine tuned" over the last two millenia. Knowledge of the fine tuning is essential yet forgotten. Never eating the soup to the bottom, we drink the broth and wonder why we're undernourished.