And you can read Lincoln's words, "First Inaugural Address, Monday, March 4, 1861":
One section of our country believes slavery is right and ought to be extended, while the other believes it is wrong and ought not to be extended. This is the only substantial dispute. The fugitive-slave clause of the Constitution and the law for the suppression of the foreign slave trade are each as well enforced, perhaps, as any law can ever be in a community where the moral sense of the people imperfectly supports the law itself. The great body of the people abide by the dry legal obligation in both cases, and a few break over in each. This, I think, can not be perfectly cured, and it would be worse in both cases after the separation of the sections than before. The foreign slave trade, now imperfectly suppressed, would be ultimately revived without restriction in one section, while fugitive slaves, now only partially surrendered, would not be surrendered at all by the other.Read it all...
Physically speaking, we can not separate. We can not remove our respective sections from each other nor build an impassable wall between them. A husband and wife may be divorced and go out of the presence and beyond the reach of each other, but the different parts of our country can not do this. They can not but remain face to face, and intercourse, either amicable or hostile, must continue between them. Is it possible, then, to make that intercourse more advantageous or more satisfactory after separation than before? Can aliens make treaties easier than friends can make laws? Can treaties be more faithfully enforced between aliens than laws can among friends? Suppose you go to war, you can not fight always; and when, after much loss on both sides and no gain on either, you cease fighting, the identical old questions, as to terms of intercourse, are again upon you.
This country, with its institutions, belongs to the people who inhabit it. Whenever they shall grow weary of the existing Government, they can exercise their constitutional right of amending it or their revolutionary right to dismember or overthrow it. I can not be ignorant of the fact that many worthy and patriotic citizens are desirous of having the National Constitution amended. While I make no recommendation of amendments, I fully recognize the rightful authority of the people over the whole subject, to be exercised in either of the modes prescribed in the instrument itself; and I should, under existing circumstances, favor rather than oppose a fair opportunity being afforded the people to act upon it. I will venture to add that to me the convention mode seems preferable, in that it allows amendments to originate with the people themselves, instead of only permitting them to take or reject propositions originated by others, not especially chosen for the purpose, and which might not be precisely such as they would wish to either accept or refuse. I understand a proposed amendment to the Constitution—which amendment, however, I have not seen—has passed Congress, to the effect that the Federal Government shall never interfere with the domestic institutions of the States, including that of persons held to service. To avoid misconstruction of what I have said, I depart from my purpose not to speak of particular amendments so far as to say that, holding such a provision to now be implied constitutional law, I have no objection to its being made express and irrevocable.
The Chief Magistrate derives all his authority from the people, and they have referred none upon him to fix terms for the separation of the States. The people themselves can do this if also they choose, but the Executive as such has nothing to do with it. His duty is to administer the present Government as it came to his hands and to transmit it unimpaired by him to his successor.