What did Lincoln mean by a house divided?

The words themselves came from Scripture — our Lord's own observation that a house divided against itself cannot stand. I applied them to the central crisis of our national life in my speech at Springfield in June of 1858, before the Republican State Convention. My meaning was precise, and Judge Douglas worked very hard to misrepresent it. As I stated that evening, “I believe this Government cannot endure permanently half Slave and half Free. 1 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” The Judge charged me with preaching a crusade, with demanding that all States be made uniform by force. That was not my argument. The division I pointed to was not a healthy variety of local customs — different soils, different climates, different industries. Those differences are, as I put it in the Quincy debate, bonds of union rather than sources of discord. The division I meant was slavery, which in the whole history of this government had never once served as a bond of union, but had always been, as I said at Galesburg, “an apple of discord and an element of division in the house” My prediction was simply this: the agitation would not cease until a crisis was reached. The nation would settle the question one way or the other. It could not remain permanently suspended between two irreconcilable principles.