Lincoln and slavery

In Lincoln's "House Divided" speech in Springfield, Illinois, he urges that something must be done about slavery, or else it will divide the nation among free states and slave states.  Leaving the issue stand for itself and play out is not an option according to Lincoln, because it will tear apart the union.  He criticizes the Nebraska Bill because it does not explicitly ban or uphold slavery in the territory.  Rather, it leaves it up to the people in the territory to decide.  Lincoln criticizes this "squatter sovereignty" and "sacred right to self government" because he knew that the Union needed clear legislation to eradicate the issue the of slavery.  Lincoln thought that if we just left it up to the people, the issue would become worse and further our problems regarding slavery and the further division of the Union. He also criticizes the Dred Scott decision because it ruled that the government could not regulate slavery anywhere.  It seems like Lincoln was arguing that we needed the federal government to legislate something that would settle this issue, and fast.  We needed a congressional mandate to solve our problems concerning slavery.  Lincoln's speech to rally the Republicans and persuade people that we needed our nation's top central authority to act distinguishes him as a powerful leader and a visionary.