According to lincoln, how does a nation make sure that free governments (democracies), "shall not perish from the earth"?

He is saying that every generation must work to preserve what was fought here and remember the sacrifices made during that day.  They gave their lives not only to protect the Union but also for the liberties of all men so everyone would be equal.  This is the best way to ensure that democracy will always be there.

i really really really really really really dont know

brainliest is someone you pick by simply clicking a button. it only shows up if there are two people that answered your question, then you decide who answer more accurately with detail and explanation and you give that person the title "brainliest".

i hope this your understandings.