Since this country's founding, some of our biggest fights have been over the question of who's covered by the timeless principles stated in the Declaration of Independence (namely, "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 pursuit of Happiness”). Who's "all men"? Who's a "person," with a right to equality before the law? African Americans? Women? Fertilized eggs? Dogs? Notions of full personhood have evolved over the last two centuries. Today's debates raise new questions about "personhood" and protection from exploitation by law, at the same time as artificial intelligence and zoology challenge us to redraw the boundaries of selfhood.