Douglas paid tribute to Lincoln as a “kind, amiable, and intelligent gentleman, a good citizen and an honorable opponent,” but took issue with Lincoln’s June 16 speech to the Illinois Republican convention that had named him its candidate for Douglas’s seat. In that speech Lincoln had famously asserted that the nation could not exist “half slave and half free.” According to Douglas, Lincoln’s assertion belied the “diversity” in domestic institutions that was “the great safeguard of our liberties.” Then as now, “diversity” was a shibboleth hiding an evil institution that could not be defended on its own terms.

Douglas responded to Lincoln’s condemnation of the Supreme Court’s Dred Scott decision — a condemnation that was the centerpiece of Lincoln’s convention speech. “I am free to say to you,” Douglas said, “that in my opinion this government of ours is founded on the white basis. It was made by the white man, for the benefit of the white man, to be administered by white men, in such manner as they should determine.”

Lincoln invited Douglas’s audience to return the next evening for his reply to Douglas’s speech. Lincoln’s speech of July 10, 1858, is one of his many great speeches, but in one respect it is uniquely great. It concludes with an explanation of the meaning of this day to Americans with incomparable eloquence and insight in words that remain as relevant now as then.

[Scott has a Part II to this post, with a reflection from Calvin Coolidge on the Declaration. Read both, but be sure to follow this link to read Lincoln’s powerful rebuttal first. — Ed]