Concerned, Determined

The basic tone of the "House Divided" speech is, "The end is nigh! But we'll definitely win." (Which is also the tone of most superhero movies when you think about it.)

Lincoln worries about the danger of the outcome of recent policies. But he claims to be confident that his side will come out on top. Cue the dramatic yet inspirational music (a little John Williams always works nicely).

Concerned

From the beginning, Honest Abe sounds honest-worried. He says, about popular sovereignty:

Under the operation of that policy, that agitation has not only not ceased but has constantly augmented. In my opinion, it will not cease until a crisis shall have been reached and passed. (4-5)

Yeeks.

And he goes on to talk about the Dred Scott case:

Under the Dred Scott decision, "squatter sovereignty" squatted out of existence, tumbled down like temporary scaffolding; like the mold at the foundry, served through one blast and fell back into loose sand; helped to carry an election and then was kicked to the winds. (43)

Double yeeks.

He declares his fear that slavery will expand everywhere throughout the speech. For instance, he declares that the language of the Kansas-Nebraska Act:

[…] is made in order that individual men may fill up the territories with slaves, without danger of losing them as property, and thus enhance the chances of permanency to the institution through all the future. (52)

Triple yeeks. The "yeeks" moments just keep coming.

Speaking to a Republican audience, made up of people who are against the expansion of slavery, Lincoln emphasizes his concern repeatedly over the real danger of that happening. Sometimes he uses logical, step-by-step outlines to provide evidence for his fear, sometimes he just waxes poetic on how much trouble they're in.

Lincoln is genuinely worried that another Supreme Court decision could stop any prohibition of slavery, and he wants to make sure his audience feels the way he does. Although given their party affiliations, they probably were on board the worry train already.

Determined

Despite the doom and gloom, Lincoln opens and closes the "House Divided" speech with notes of hope. Their side can and will prevail if they stay strong.

Although the "house divided" can't last, Lincoln says:

I do not expect the Union to be dissolved; I do not expect the house to fall; but I do expect it will cease to be divided. It will become all one thing, or all the other. (8-9)

Yeah, it ain't exactly a shining beacon of hope, but he's so sure that the situation will go one way or the other, you can't help but believe him.

The really determined Lincoln comes out at the end of the speech. He reminds the audience of how strong the Republican Party has become, and how it has weathered the storm against the powerful, wealthy slaveholding establishment. He ends the speech like this:

The result is not doubtful. We shall not fail – if we stand firm, we shall not fail. Wise councils may accelerate or mistakes delay it, but, sooner or later the victory is sure to come. (124-126)

Lincoln's final thought is one that he and his audience can stem the tide and be victorious in the face of the danger he expressed so much concern about. It really wants to make you stand up and clap. Or shed a few patriotic tears. Or both.