Lincoln made this statement in 1858 as he campaigned for the United States Senate. He was running against Democrat Stephen A. Douglas. Douglas staked his run on the claim that a compromise could be found between free states and slaves states.

In his speech, Lincoln opposed Douglas and came down decisively against the idea that the United States could stay a mixture of free and slave states. He asserted that it had to go one way or another, and it would end up either entirely slave-holding or entirely free. He said:

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 it will cease to be divided. It will become all one thing or all the other.

In referring to a "house divided," Lincoln alludes to a Biblical passage in Matthew, chapter 12. In this section, Jesus heals a man who is blind and mute. The people are amazed, but the Pharisees say that Jesus's healing power is Satanic, coming from demons. Jesus says that is impossible, because Satan would not hurt his own cause by doing good. Jesus states:

Every kingdom divided against itself will be ruined, and every city or household divided against itself will not stand.

Alluding to the Bible adds weight and authority to Lincoln's words. Lincoln means by his statement that a nation cannot survive while it is doing both good and evil at the same time. The forces of good and evil will continue to clash, weakening the country. Some resolution must come, or the whole nation will collapse under the weight of its own contradictions.