One of the longest standing mottos for the United States is E Pluribus Unum - from many, one. It's long been thought to mean much more than the formal and legalistic concept of a union of states - it's been thought to mean a uniting into a civil society of peoples of many kinds. And indeed, it's indisputable that the American people are of many kinds. But today many speak of a new age of American tribalism. On both the left and the right, in different ways, there is both the feeding of, and feeding on, differences and divisions among groups of Americans. Are politics highlighting differences among Americans a sign of progress - ferreting out historical wrongs and establishing protection for new expressions of rights - or are we becoming once more, as we were in the lead-up to the most terrible civil war experienced in modern times in a Western nation, what Lincoln called "a house divided against itself"? Guests: Michael Arceneaux, a Houston-bred, Howard University-educated writer and author who covers issues related to culture, religion and racial politics; Andrew Sullivan, an English-born American author, political commentator and former editor of the conservative publication The New Republic.