The usage of the word, Beautiful, used in the third to last line in I, Too, Sing America, does not mean outer beauty. Beautiful is indeed trying to express the trueness and importance of inner beauty, and how sometimes, when people are caught up in discriminating against people who aren't like them, they pass over this important part of acceptance. Langston Hughes is trying to show that some day white people will see how beautiful he is, being black. He is trying to show that now (when he was writing this poem), white people think black people are ugly. That they have no inner beauty and don't deserve as many right as white people. Hughes then uses the word beautiful in a sentence which gives the sense that this usage is for a future day, when white people will see how truly beautiful and equally important black people really are.
 

To lean more about the author of this poem, Langston Hughes, visit The Academy of American Poets at
                           http://www.poets.org/poets/poets.cfm?prmID=84

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