According to John O'Sullivan, what feature is usually a strong indicator of a nation's greatness, longevity and quality of life of its people?Why...

In an 1839 essay entitled "The Great Nation of Futurity",
John O'Sullivan argued that equality among all citizens is the most important indicator
of a nation's future prosperity.  O'Sullivan is probably best known for coining the term
"manifest destiny", first in an article arguing in favor of the annexation of Texas, and
later in another article arguing in favor of the United States position in the dispute
with Great Britain over the Oregon territory.  O'Sullivan's arguments were based on his
idea that the United States had a unique mission assigned by none other than God himself
to extend republican democracy from the Atlantic to the Pacific Ocean.  Of course, many
in favor of the territorial expansion of the United States couldn't wait to jump on the
"manifest destiny" bandwagon once the Almighty was invoked as an integral part of the
reason for expansion.