The word “dedicate” is one of the most important words in Abraham Lincoln’s Gettysburg Address. One reason he uses this specific word is because his speech was delivered as part of the ceremony to dedicate a cemetery for the fallen soldiers of the battle. Its importance is emphasized by the numerous repetitions—it appears five times—and by the positive and negative meanings that he imparts to it. Furthermore, he substitutes a different word, “consecrate,” and repeats that as well.
In paragraph 2, he uses the word to convey the function of the United States and of its peoples: “that nation, or any nation so conceived and so dedicated...” He then draws the concept close to his use of “we” to mean the American people, and reminds the audience why they are there: "We have come to dedicate a portion of that field....”
However, he changes the focus and attracts their attention by negating that statement. The third paragraph begins:
But in a larger sense, we can not dedicate—we can not consecrate—we can not hallow—this ground. The brave men, living and dead, who struggled here, have consecrated it....
With this surprising negation, Lincoln also introduces an implicit question—if we cannot dedicate it, what can we do? Further, by changing first to “consecrate” and then to “hallow,” Lincoln adds a religious connotation, then builds on that by saying that the soldiers themselves “have consecrated” the ground.
He continues with a rhetorical device to add emphasis, that of anaphora, the repetition of a word, phrase, or clause at the beginning of two or more sentences. He begins two sentences almost the same:
It is rather for us to be here dedicated...
It is for us the living, rather, to be dedicated here....
These sentences also answer his implicit question and encourage the audience to take up the “great task” he lays out, uniting the nation.