A house divided against itself cannot stand. This quotation reflects Lincoln's belief that?

Answer: the United States would have to become either all slave or all free.

house refers to the Union and what causes the division was between the opponents and advocates of slavery

Explanation:

Lincoln felt that the ideals of freedom for all and the institution of slavery could not coexist morally, socially, or legally under one nation. Slavery must ultimately be universally accepted or universally denied.

Lincoln's saying that there is no compromise You have got to be on one side or the other.' In effect, he's saying, 'I'm on the side of freedom and Stephen Douglas is on the side of slavery

Some interpreted the statement that Lincoln was actually calling for a civil war instead he meant that a part of the country cannot be half free and the other totally free