How does the author use metaphor in the nonfiction book, The White Album?

The Grace Episcopal Cathedral in San Francisco is a real place that acts as a metaphor in Didion's essay 'James Pike, American' as it forms one of the interesting facts about the man's life who famously 'completed it.'

The Grace Cathedral itself was a monument of the Episcopalian faith that was famously 'never completed' and Didion remembers the fact that she, her mother and her grandmother used to collect pennies to go towards the building effort of the Cathedral. The act of supporting its development becomes a metaphor for the never ending pursuit of perfection in the American psyche, (and also of collective community endeavor). The fact that James Pike announced it finished Joan finds disturbing and somehow missing the point.