In his fourth of july speech why does douglass say to his audience that the fourth of july is yours not mine

On July 5, 1852, Douglass gave a speech at an event commemorating the signing of the Declaration of Independence, held at Rochester's Corinthian Hall. It was biting oratory, in which the speaker told his audience, "This Fourth of July is yours, not mine. You may rejoice, I must mourn."

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