How we cite our quotes: (Sentence)
Quote #1
Either the opponents of slavery will arrest the further spread of it and place it where the public mind shall rest in the belief that it is in the course of ultimate extinction, or its advocates will push it forward till it shall become alike lawful in all the states, old as well as new, North as well as South.
Have we no tendency to the latter condition? (10-11)
Early on, Lincoln introduces the idea that will occupy much of his speech. There is a real chance that the U.S. will become 100% slave states. If his audience thought that impossible, he will soon present a laundry list of evidence to prove the opposite.
Quote #2
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)
On the surface, popular (or "squatter") sovereignty might seem like a very reasonable, fair approach to dealing with slavery in the new states. Lincoln's unusually poetic language here tells us not to get our hopes up, because that method of resolution has completely failed. When such a democratic and theoretically reasonable policy is so demolished, what hope is there to solve the problem? Not to mention how quickly it all fell apart—which implies that more could be destroyed just as quickly.
Quote #3
Second, that, "subject to the Constitution of the United States," neither Congress nor a territorial legislature can exclude slavery from any United States territory. This point 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. (51-52)
Lincoln consistently reminds his audience what's at stake here: the ability to prevent the slaveholding elite of the South from invading their northern territories. He's describing the outcome of the Dred Scott decision, indicating that the Supreme Court has taken the country one big step closer to this scenario. By painting a picture of the potential future, Lincoln gives his audience a picture to visualize that would strike fear into any 1858 Republican voter.