One wintry morning recently I pushed my shoes into my galoshes, in a hurry to make the bus, when I noticed the ill-fitting consequences of putting the right overshoe on my left foot and the left one on my right foot. As I grumbled about haste making waste a memory came rushing in. I was standing in our grade school gym, listening to my basketball coach explain to me the importance of keeping my toes pointed in and not splayed out when running up and down the court. “It’s probably all of those hills that you climb on your farm,” the coach told me, “and thus you run all klutzy-like.” The recommendation to “think pigeon-toed” worked. I gained more agility due to a perceptive coach’s simple advice.

Being an introspective person, I was spurred by that memory into an extended reflection about toes and feet. Why is it that the line from the big toe to the little toe is angled, necessitating a shoe design that differentiates between left and right? Then I recalled reading somewhere about how the triangle is the most stable shape in nature.

My rumination continued as I headed for the bus stop. So the feet are constructed in a way that, like the triangle, makes them more stable in moving the body forward. With greater stability there is increased agility. I thank God that, even despite being in this fog of contemplation, I made the bus that morning and also thank Him for the wisdom behind even this small detail of His creation.

Early in January of this year, Pope Benedict XVI addressed the Vatican diplomatic corps, emphasizing the need to protect all of God’s creation. The Holy Father referred to the importance of a sound ecology to avoid further damage to the world’s water, air, soil and vegetation. But the pope’s remarks extended beyond what we might think about when we hear of this topic, such as oil spills, smoke stacks, junk yards, and buzz saws in a rain forest.

According to Benedict, caring for natural ecology must be linked with a regard for human ecology. He told his audience that “this concern and commitment for the environment should be situated within the larger framework of the great challenges now facing mankind” which included not only threats to nature but also legal attacks against the unborn, the devastation of war and poverty, and the redefinition of marriage. It was his reference to the last issue that sparked the most heated public reaction to his address.

The pope stated that “[c]reatures differ from one another and can be protected, or endangered, in different ways, as we know from daily experience. One such attack comes from laws or proposals which, in the name of fighting discrimination, strike at the biological basis of the difference between the sexes. I am thinking, for example, of certain countries in Europe or North and South America” wherein same-sex relationships have been granted marital or civil union status.

This column that you are reading was written in mid-January 2010, when a federal judge in California was conducting a trial on the issue of same-sex marriage in the case of Perry v. Schwarzenegger. The lawsuit was filed by same-sex couples asking the federal courts to strike down Proposition 8, a ballot measure approved by California voters in 2008. Proposition 8 amended the state constitution by defining marriage as the union of one man and one woman.

Litigators expect the California case to eventually reach the United States Supreme Court. The plaintiffs hope the nation’s highest court will make same-sex marriage legal in every state as a constitutional mandate.

One of the issues at trial concerned whether there are any relevant differences between men and women and between opposite-sex and same-sex couples, especially regarding parenting. This issue is important because it touches not only on the well-being of children but also because it goes to the root of the argument about why society and the Catholic Church have supported the traditional definition of marriage as a matter of human ecology.

The word “ecology” comes from a Greek word meaning “house.” Marriage has been understood by society as the “house,” so to speak, of the most fundamental human difference that we know of, the difference between the sexes. What happens to human ecology when, by redefining marriage, sexual difference is ignored as if irrelevant or denied as if non-existent?

Anthropologist Margaret Mead observed in her 1949 book “Male and Female” that “[w]e know of no culture that has said, articulately, that there is no difference between men and women except in the way they contribute to the creation of the next generation.” Based on her historical studies, she concluded that “[t]he differences between the sexes is one of the most important conditions upon which we have built the many varieties of human culture that give human beings dignity and stature.”

From the secular perspective, as captured in the motto included in our national seal which reads “E pluribus Unum” or “out of the many, one,” and found in the words of the preamble to the United States Constitution, with its commitment “to form a more perfect union,” recognizing and incorporating differences is essential to creating unity. Even the United States Supreme Court has acknowledged in another context that communities consisting of both sexes add something essential to society and are worthy of celebration given the “inherent differences” between the sexes (United States v. Virginia, 1996). Redefining marriage negates that common-sense view.

Like the early stages of a chemical leak, it is too early to determine all of the sociological ramifications of an experiment in Massachusetts and elsewhere that ignores or denies sexual difference in society’s most basic human institution. In his talk to the Vatican diplomats, Pope Benedict warned of harm already evident on a spiritual plane: a pride or hubris that denies God’s place by failing to acknowledge in the marital institution “the structure willed by the Creator.”

Daniel Avila is the Associate Director for Policy and Research of the Massachusetts Catholic Conference.