Lincoln's true position on slavery has been argued far and wide, sometimes with the claim that he was not against it. While it is never possible to know exactly what is in another person's heart, evidence exists that Lincoln was always opposed to slavery, thouhg his feelings about it certainly became stronger after he became president  Here is a small piece of evidence of his opinion.

If A can prove, however conclusively, that he may, of right, enslave B—why may not B snatch the same argument, and prove equally, that he may enslave A?

You say A is white, and B is black. It is color, then;—the lighter, having the right to enslave the darker? Take care. By this rule, you are to be slave to the first man you meet, with a fairer skin than your own.

You do not mean color exactly?—You mean the whites are intellectually the superiors of the blacks, and, therefore have the right to enslave them? 

Take care again. By this rule, you are to be slave to the first man you meet, with an intellect superior to your own.

But, say you, it is a question of interest; and, if you can make it your interest, you have the right to enslave another. Very well. And if he can make it his interest, he has the right to enslave you.

History 121 Part 4