A long discussion of this problem from a philosophy professor at Notre Dame. If you read the paper, which is about 5 pages long, your own analogy may come to mind.
METAMIA is a free database of analogy and metaphor. Anyone can contribute or search. The subject matter can be anything. Science is popular, but poetry is encouraged. The goal is to integrate our fluid muses with the stark literalism of a relational database. Metamia is like a girdle for your muses, a cognitive girdle.