President barrack obama cites the declaration of independence when he states "we hold these truths to be self-evident, that all men are created equal; that they are endowed by their creator with certain unalienable rights; that among these are life, liberty, and the suit of happiness." why does he use this quote in the beginning of his speech?

one of the central themes of edward abbey's work has been his staunch opposition to the glen canyon dam on the colorado river that created lake powell, destroying stunning scenery and wildlife habitat, endangering many rare species of fish and animals, and also irreparably destroying many important archaeological sites which provided information about the early inhabitants of the united states.