why did lincoln state that they could not dedicate the cemetary?

Answer 1

"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, far above our poor power to add or detract."


He didn't say it quite that way, what he meant is that it was hallowed ground that the men through their lifes and thier death have consecrated it.

Answer 2

Please actually read the Gettysburg Address - it is short - one of the shortest in American History. Your answer lies in the VERY NEXT 2 SENTENCES after "But, in a larger sense, we can not dedicate—we can not consecrate—we can not hallow—this ground".

I could easily tell you, but I think its important that you read it.