In my mind, the largest and most credible part of King's speech was the idea that Civil Rights and the advancement of racial equality was part of American History. Throughout the speech, Dr. King uses these ideas to emphasize his point. For example, the fact of the "100 years later" is a direct reference to President Lincoln's Emancipation Proclamation, where slaves were released from bondage. Dr. King's references to both Jefferson's Declaration of Independence as well as the Constitution are also notable. The idea of "a promissory note" being given to people of color is a passionate way of explaining how American History supports Dr. King's cause. The idea of being able to use American historical narrative as evidence or proof of why the dream must be achieved is another notion of credibility within the speech. In this light, Dr. King's argument gains credence as he argues that Civil Rights is nothing more than an extension of the rights upon which the nation was founded.
The tradition of public eloquence can be observed in Martin Luther King, Jr.’s stirring, perceptive and incantatory “I Have a Dream” speech. Seldom has the plea that America might fulfill its promise of freedom and equality for all its citizens been stated with such majesty. Aware of his need to reach many different constituencies with this one speech, King draws together references from the Bible and the Emancipation Proclamation, along with ideas of nonviolent protest, in a series of stirring metaphors that allude to ideas held sacred by all. King recognizes that there are different groups of people in his audience, not only blacks but whites as well. In talking of the fight for equality, he employs a range of appeals directed at different groups.