This week, the United States Senate will take the first step in deciding who gets to define marriage for the entire nation: activist judges - or the American people.

Although not the final vote on marriage by any means, the vote your senator casts this week gives a clear signal on how much he trusts you and your fellow citizens to determine the defining issue of our generation. A vote against the amendment means your senator is willing to allow activist judges to make the decision for you.

A little background on how we got to his point is helpful. In 1996, a liberal state court in Hawaii threw out that state's laws against same-sex marriage. Lawmakers around the nation knew that if a few judges in Hawaii could destroy the traditional definition of marriage, judges anywhere could and would do it. Within months, a law that defines marriage for the federal government as the union of one man and one woman, and prevents states from being forced to recognize contrary definitions - which lawmakers thought would solve the problem - passed both houses of Congress by veto-proof majorities and was signed by President Clinton.

It was called the Defense Of Marriage Act, and it caught on like wildfire. Within eight years, 38 states had adopted their own DOMAs, and five other states had inserted DOMA language into other laws.

Many thought the issue was settled once and for all, but, again, activist judges - this time in Massachusetts - took power away from the people of that state and declared same-sex marriage legal. Other activist officials started thwarting the will of the people and breaking the laws in their states and began issuing same-sex licenses. Homosexual couples from many states traveled to Massachusetts to be "married" - mayhem resulted.

Exclusive: Today, Americans are rising up to make their voice of reason heard - citizens in Michigan, Montana, Arkansas and Oregon have gathered enough signatures to put state constitutional amendments protecting marriage on the fall ballots, and North Dakota and Ohio are close. Michigan organizers expect the measure to pass by a 2-to-1 margin or more, with 80 percent of Republicans and more than half the Democrats in the state planning to support it.

In seven other states - Georgia, Kentucky, Louisiana, Mississippi, Missouri, Oklahoma and Utah - legislators voted to put pro-marriage amendments on ballots this fall. To find out where your state stands and to get a full state-by-state accounting, simply log on to heritage.org.

American citizens seem to understand instinctively what's at stake here. Marriage has meant one man and one woman in every successful nation on Earth since the beginning of mankind. Marriage is about propagating not just the human race, but also the values of a society, the difference between right and wrong.

By promoting social order, it creates a safety zone for the man and woman involved as well as for their children. A raft of social science research shows that children who grow up in households where the mother and father are married have the best chance at a good life. They earn more, learn more, get in trouble less and have fewer problems with drugs, alcohol or abuse.

Unfortunately, many of the senators ready to debate the amendment this week do not understand its importance. Thanks to the efforts of Sens. Wayne Allard, R-Colo., Sam Brownback, R-Kan., and Zell Miller, D-Ga., and their co-sponsors, senators at least will get the facts, and will be forced to take a stand on whether or not they believe the issue is even worth debating.

Many senators say they oppose same-sex marriage, but don't see the purpose in an amendment. Perhaps these senators are just afraid to take a stand. But when a few activists judges around the nation are determined to redefine this most basic of human institutions through court decisions which thwart the will of the people, our elected officials must take a stand on whether or not they believe voters should determine this issue for themselves. Unfortunately, we've now reached the time where the only way - I repeat - the only way to protect marriage and civil society as we know it is to pass a constitutional amendment defining marriage as a union between one man and one woman.

Redefining marriage - the most basic of human institutions - is akin to reprogramming the DNA of a nation. This week is a crucial one in who will determine our future.

Rebecca Hagelin is a vice president of The Heritage Foundation.