Human action can be modified to some extent, but human nature cannot be changed. There is a judgment and a feeling against slavery in this nation, which cast at least a million and a half of votes. You cannot destroy that judgment and feeling — that sentiment — by breaking up the political organization which rallies around it. You can scarcely scatter and disperse an army which has been formed into order in the face of your heaviest fire; but if you could, how much would you gain by forcing the sentiment which created it out of the peaceful channel of the ballot-box, into some other channel?

Cooper Union speech (1860)