Lincoln wanted to save the Union at all costs. In the letter response to Horace Greeley, Lincoln stated that he did not agree with those who would not save the Union unless they could save slavery at the same time. His stated object was to save the Union, not to save or destroy slavery. "If I could save the Union without freeing any slave, I would do it; and if I could save it by freeing all the slaves, I would do it; and if I could do it by freeing some and leaving others alone, I would also do that." Whether Lincoln hurt or helped the slaves, it was all for the sake and well-being of the Union. "The sooner the national authority can be restored, the nearer the Union will be 'the Union as it was.'"
President Lincoln was unbiased and open-minded to ideas involving the saving of the Union. "I shall try to correct errors when they are shown to be errors; and I shall adopt new views as fast as they shall appear to be true views." Basically, he will do anything he can to help the cause. Even though Lincoln tried to hear and respond to the nation's wishes, he had to favor the rejection of the doctrine of popular sovereignty. (Electronic Resource) A possible explanation for this decision may have been that he felt the government was better equipped to decide on the fate of the country (at war within itself over the issue of slavery.)
Lincoln saw his duty as helping his people and restoring the Union. His country was his main priority. He took this responsibility seriously stating," I intend no modification of my oft-expressed personal wish that all men, everywhere, could be free." Written in the Emancipation Proclamation of 1863, Lincoln deemed,"...all persons held as slaves within any State, or designated part of the State, the people whereof shall then be in rebellion of the United States...forever free." In his power of Commander-in-Chief of the Army and Navy of the United States Lincoln had to suppress fighting. His duty required him to call for the freedom of the slaves in time of actual armed rebellion against the authority of the Government.
From the above sources, Lincoln has shown to be true and fair to his duties and his country on the issue of slavery. His main goal was to save the Union at any cost. He not only saved the Union, but freed the slaves also.