I should like to know if, taking this old Declaration of Independence, which declares that all men are equal upon principle, you begin making exceptions to it, where will you stop? If one man says it does not mean a Negro, why not another say it does not mean some other man?

In this quote, Abraham Lincoln addresses the principle of equality outlined in the Declaration of Independence. He questions the logic of making exceptions to the claim that all men are created equal, suggesting that if one group is excluded—such as Negroes—then there is no end to the exclusions that could follow. Lincoln warns that once the principle of equality is undermined, it could be used to justify inequality for any other group, which threatens the very foundation of freedom and justice in a democratic society.

Lincoln’s argument is centered on the idea that if equality is a fundamental right, it must be universal and not subject to arbitrary exceptions. By pointing out the dangerous consequences of making exceptions, Lincoln emphasizes the importance of consistency in the application of principles. To allow one group to be excluded from equality could lead to a slippery slope, where others might similarly be denied their rights, thereby undermining the integrity of the nation’s ideals.

The origin of this quote comes from one of Lincoln’s public speeches, where he argued against the expansion of slavery and for the inclusion of African Americans in the promise of equality in the United States. As a leader dedicated to preserving the Union and ending slavery, Lincoln understood that the Declaration of Independence was a powerful symbol of the nation's commitment to equality. He used this quote to challenge those who sought to justify slavery by claiming that African Americans were excluded from the declaration’s promise.

In this context, Lincoln’s words are a powerful reminder that the principles of equality and freedom cannot be selectively applied. His plea is for consistency in upholding the core values of the nation, arguing that to exclude one group from those values is to jeopardize the future of liberty and justice for all.