What comment does the author make through the analogy at the end of this paragraph?

great geniuses have the shortest biographies. their cousins can tell you nothing about them. they lived in their writings, and so their house and street life was trivial and commonplace. if you would know their tastes and complexions, the most admiring of their readers most resembles them. plato, especially, has no external biography. if he had lover, wife, or children, we hear nothing of them. he ground them all into paint. as a good chimney burns its smoke, so a philosopher converts the value of all his fortunes into his intellectual performances.
(from representative men by ralph waldo emerson)

plato did not want to have a family or a significant role in society.

plato's obsession with philosophy was a major impediment to his social life.

the ideas that philosophers expound are the most notable aspects of their lives.

philosophers essentially think alike despite the differences in their fortunes.