WHEN ABRAHAM Lincoln spoke at Gettysburg of "our fathers" bringing forth a new nation, he could be confident that his audience would understand and respond to that term, with its implication of common origins and outlooks. Could a president speak so easily in the same way today? In 1863 the crowd that gathered to hear the president was basically homogeneous in race, religion and so on -- not far removed from the Founders of four score and seven years before, and in some instances no doubt able to claim literal descent.

Contrast that scene with the mix of hues, languages, accents, dress styles, hairdos and T-shirt messages likely to compose any similar great crowd of Americans (as well as a fair number of would-be Americans) that might gather to hear a president today. Could a Lincoln speak with such assurance of "our fathers" as he did 136 years ago? Is there still common ground in this extraordinarily fast-moving, diverse, ever changing and, in many ways, separated society?

The question isn't exactly new. It was stated most eloquently by Lincoln as he stood on ground that only five months before had been soaked with the blood of more than 50,000 Americans -- dead and wounded -- in a country that had been warring with itself for more than two years and was far from the end of its conflict. Could such a nation endure? he asked.

It has endured that war and a great deal more, but in a country based on such grand concepts as liberty, equality and openness to new ideas and people, union is going to be a never-ending effort. The key to maintaining it may well be found in another Lincoln speech, delivered five years before Gettysburg (it was brought to our attention by Richard Estrada of the Dallas Morning News). "We have among us . . . perhaps half our people who are not descendants at all" of the Founding Fathers, Lincoln said in an 1858 address on the meaning of the Fourth of July; ". . . but when they look through that old Declaration of Independence, they find that those old men say that `We hold these truths to be self-evident, that all men are created equal,' and then they feel that the moral sentiment taught in that day evidences their relation to those men, that it is the father of all moral principle in them, and that they have a right to claim it as though they were blood of the blood, and flesh of the flesh, of the men who wrote that Declaration, and so they are."

And so are we all, through eruptions of fireworks past, present and future.