WITH NEARLY two decades gone since the assassination in Memphis of Martin Luther King Jr., each celebration of the national holiday in his honor takes on more meaning. Today's young adults and all the children they have brought into the world cannot recall in the same way as their elders what it was across the land that inspired the mighty message of Dr. King. Now this day in January affords all Americans at least a moment to be reminded of old, ugly divisions and violence -- and perhaps even to ponder the persistent injustice of racism that continues to spell the considerable difference between that "dream" and reality.

True, many of the stark, openly brutal manifestations of racial intolerance have subsided, but is there anyone who believes that all Americans are "free at last" in a land without the barriers of bigotry? But a grand part of Dr. King's enduring message is its affirmation above all of patriotism, faith, love and -- yes -- impatience: "For years now I have heard the word 'Wait!' It rings in the ear of every Negro with a piercing familiarity. This 'wait' has almost always meant 'never.' "

And though his dream is still only that, his optimism can and should still stir Americans of all colors to "keep on keeping on," until that time when "we will be able to adjourn the councils of despair and bring new light into the dark chambers of pessimism and then, on that new day, when that day comes, the fears of insecurity, the torments of frustration and the doubts clouding our future, will be transformed into confidence, into excitement to reach new goals, and in which the brotherhood of man will be undergirded by secure and expanding prosperity available to all."

The magnificent simplicity of Dr. King's hopes -- and demands -- rings loudly still, a rich legacy that this annual observance calls up for renewed attention.