Final answer:
Martin Luther King Jr. primarily utilizes ethos and pathos in the given line from his "I Have a Dream" speech, appealing to credibility and emotions, with an element of logos as he offers a logical argument for nonviolent resistance.
Step-by-step explanation:
In Martin Luther King Jr.'s "I Have a Dream" speech, the appeal used is mostly ethos and pathos. King establishes his credibility (ethos) by presenting himself as a moral and disciplined leader, urging his followers to conduct their struggle with dignity and discipline. However, the primary appeal is pathos, as he evokes emotions by speaking of justice, freedom, dignity, and the higher moral ground of conducting nonviolent resistance. The use of words like 'warm threshold,' 'palace of justice,' and 'majestic heights' appeal to his audience's emotions and shared values. There is also an underlying element of logos as he presents a logical argument for nonviolence being the more effective path to justice, though this is not the dominant appeal in this particular line.