The metaphor is perhaps one of man's most fruitful potentialities. Its efficacy verges on magic, and it seems a tool for creation which God forgot inside one of His creatures when He made him. All our faculties keep us within the realm of the real, of what is already there. The most we can do is to combine things or break them up. The metaphor alone furnishes an escape; between the real things, it lets emerge imaginary reefs, a crop of floating islands.