Final answer:
Martin Luther King Jr. introduces his argument by referencing historical context and highlighting the persistent racial inequalities, setting the stage for a call to action for racial equality.
Step-by-step explanation:
Martin Luther King Jr. introduces his argument in his seminal text 'I Have a Dream' with historical context and a portrayal of the current state of racial inequality. He begins by referencing the Emancipation Proclamation, which symbolizes a great beacon light of hope to millions of Negro slaves.
However, he points out that 100 years later, African Americans are still not free and live in a society characterized by segregation and discrimination. King's introduction sets the tone for his argument, which is that despite some progress, significant change is still necessary to achieve racial equality.