The catchy Beatles tune, "Love Is All You Need," is actually being played out today in the U.S. Supreme Court. Indeed, it is one of the central grounds upon which the case for gay marriage is being made. But in real life, there is a whole lot more to marriage than love. 
Not only is love as a basis for marriage a relatively recent phenomenon—most marriages throughout history were arranged or based on duty—it is profoundly detached from the historical purpose of marriage, which is procreation. Once love is given primary status as a condition for marriage, the institution itself is no longer recognizable. 

It was love that motivated three men to "marry" in Thailand on Valentine's Day. As one of the "spouses" said, "Love occurs unconditionally and is not limited to only two people." Ten years ago, two women and a man "married" in the Netherlands. The man said, "I love both Bianca and Mirjam, so I am marrying them both." Allen and Patricia Muth tried to marry in Wisconsin in 1997 but were blocked by the courts (they lost again in 2005), even though they have four children together. Allen and Patricia are brother and sister. 
If "Love Is All You Need," then the Muths have been treated unjustly and should be released from prison. 

Baltimore Archbishop William Lori, chairman of the bishops' Ad Hoc Committee on Religious Liberty, accurately identifies the problem. He notes that "when you redefine marriage as many people want to do today it becomes more a relationship of affection, an emotional relationship." He understands that marriage is about families, and that children need a mother and a father—not two mothers or two fathers. Just ask Heather Barwick, who is party to a brief against gay marriage today. She was raised by two mothers, who, though loving, could not give her something she needed, namely, "the need for a father." Heather is living testimony that "Love Is Not All You Need."