“Fourscore and seven years ago our fathers brought forth upon this continent a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal.”

But the sin of slavery was written into America’s Constitution, leading to “a great civil war, testing whether that nation, or any nation so conceived and so dedicated, can long endure.”

This April, as we commemorate the anniversary of the attack on Fort Sumter, our national attention wanders silently back 150 years to the second-bloodiest outbreak of collective insanity in our nation’s history, a conflict that nearly tore it apart.

It happened because some Americans were willing to fight to the death for the “right” to deprive others of their freedom. They were non-persons, it was said — the Supreme Court agreed in a 7-2 decision — and their owner could freely and legally exercise the right to keep or even kill them. The opposition was merely seeking to “impose their own morality.”

The cost to redeem America’s original sin still appalls us, and well it should: just over half a million lives, mostly young ones.

As we watch the anniversaries of the days seared into our national memory slowly reel by over the next four years, with ghastly names like Gettysburg, Chancellorsville, Antietam, Bull Run and The Wilderness, will we learn the lessons of the Civil War?

Will we learn what Abraham Lincoln told Congress in 1862? “In giving freedom to the slave, we assure freedom to the free.”

Will we agree with his 1864 letter to A.G. Hodges? “If slavery is not wrong, nothing is wrong.”

Because if we do, then may the bitter remembrance of Harpers Ferry and Cold Harbor and Savannah and Fredericksburg and Vicksburg and Appomattox chasten our hearts to realize that we still shed our brothers’ blood. Our nation lives today in the most abhorrent collective insanity ever to grip a civilized nation. Systematically trampling the rights of others — blacks or Jews — is mind-bogglingly evil, and yet we have created legal fictions to justify immolating nearly 50 million of our own sons and daughters — non-persons with no legal rights — to the idols of “rights” and “choice” on the grisly altars of our abortionists’ tables since 1973. That’s eight times the Holocaust and practically 100 times the Civil War.

This, of course, is a laughing matter, at least for Jon Stewart on the March 9 episode of Comedy Central’s The Daily Show, satirizing former Sen. Rick Santorum’s public comparison of abortion to slavery. “If politicians are so concerned about what’s killing black people, how about curing diabetes or sickle cell? Or ban something that kills us on the inside: Tyler Perry’s House of Payne,” one actor suggested to Stewart.

Here’s why. In 2007, the most recent full data available from the Centers for Disease Control, 12,459 African-Americans died of diabetes and 970 died of various forms of anemia in America. The pro-abortion Guttmacher Institute reports that 363,000 children of black mothers were aborted here in 2008. That’s nearly 30 times the death rate from diabetes and 375 times the death rate from anemia. Why that should provoke in-studio hilarity is beyond us.

Even more disturbing: The Atlantic senior editor Ta-Nehisi Coates, who is black, wrote in criticism of Santorum that the slavery-abortion analogy breaks down because slaves were not “denied the right to exist.” We’re pleased to concede his point. He then went on to say that slavery can’t be reduced to “the simple act of slave-holding,” since it fueled America’s economic growth in the early 19th century: “In terms economic, cultural and political, slavery made America possible.” (So might makes right?) The truly jaw-dropping conclusion he draws is that Santorum — and implicitly us — is “dishonest” and racist.

But if we give freedom to the unborn, we assure freedom to the free. If abortion is not wrong, nothing is wrong. And no one really desires to have been aborted. Lincoln was right.

And perhaps he will be right again. Well did he prophesy to the Republican Convention in 1858 that “a house divided against itself cannot stand. I believe this government cannot endure permanently half slave and half free. I do not expect the Union to be dissolved; I do not expect the house to fall; but I do expect that it will cease to be divided.” It happened once. By God’s grace, may it happen again.

We’re sick of writing editorials about abortion. Someday the day will dawn when America is finally cured of this collective insanity too, but until it does, “with malice toward none, with charity for all, with firmness in the right as God gives us to see the right, let us strive on to finish the work we are in, to bind up the nation’s wounds … to do all which may achieve and cherish a just and lasting peace among ourselves and with all nations.”