Read Lincoln's discussion in the Sixth Lincoln-Douglas debate on the existence of slavery in the United States.

What does Lincoln think of slavery and the potential for its spread? How does Lincoln think the problem should be addressed?

"We have in this nation this element of domestic slavery. It is a matter of absolute certainty that it is a disturbing element. It is the opinion of all the great men who have expressed an opinion upon it, that it is a dangerous element. We keep up a controversy in regard to it. That controversy necessarily springs from a difference of opinion, and if we can learn exactly—can reduce to the lowest elements—what that difference of opinion is, we perhaps shall be better prepared for discussing the different systems of policy that we would propose in regard to that disturbing element.

I suggest that the difference of opinion, reduced to its lowest terms, is no other than the difference between the men who think slavery a wrong and those who do not think it wrong. The Republican party think it wrong—we think it is a moral, a social, and a political wrong. We think it is a wrong not confining itself merely to the persons or the States where it exists, but that it is a wrong in its tendency, to say the least, that extends itself to the existence of the whole nation. Because we think it wrong, we propose a course of policy that shall deal with it as a wrong. We deal with it as with any other wrong, in so far as we can prevent its growing any larger, and so deal with it that in the run of time there may be some promise of an end to it."