It is often said that libertarianism would be fine, if not for children and foreign policy.  The point is not to pick on libertarianism, but to inject common sense into the naïve effort to move traditional marriage toward an adult contracting model, enterable by all sorts of non-traditional actors.

Specifically, there is a Gnostic impracticality in the vain pretense that children can be loved and raised just as well under an adult-contracting arrangement as within a real, traditional, and physical family unit. 

The re-packagers of marriage fail to grasp this because they are self-focused.  A contractual approach is unjust.  More children will be hurt, and more will die.  Jennifer Morse explains:

We can't begin our lives as objects to which other people have rights, and somehow, magically, become persons with rights of our own. Yet, the redefinition of parenthood is doing precisely this: treating children as objects. The idea of "contract parenting" is becoming the new institutional structure proposed by people who want to "get the government out of the marriage business." Under this concept, two or more adults negotiate among themselves for parental rights.

Perhaps the sperm donor will be a friend of the lesbian couple. They all agree he will be called "uncle" and get to see the child once a week. Or perhaps one woman will "donate" the egg, which is implanted in another woman's womb. The women agree that they will both be mothers, and exclude the anonymous sperm donor father.

Andrea Maccarini refers to the "postreligious West as an ethically neutral domain deprived of any substantive notion of the good,"¹ and this is evident in adult contracting's obliviousness to child welfare.  This loss of the common good is rooted in the 1,900-year old heresy of Gnosticism, a currently thriving philosophy.  Father Neuhaus explains²:

The core gnostic impulse is the belief that we are not really part of creation, that we are not really creatures.  Put differently, it is the refusal to accept that we are not God. ... [T]he quintessence of original sin, as it is reflected in gnosticism, is the desire to be like God on our own terms.

Harold Bloom calls Gnosticism "the American religion"³:

The American Religion is pervasive and overwhelming ... even our secularists, indeed even our professed atheists, are more Gnostic than humanist ... each of us is subject and object of the one quest, which must be for the original self ... that we are convinced goes back to before the Creation.

Neuhaus describes it as "this lofty sense of being spiritually untouched and untouchable by the grubby stuff of what lesser minds call the real world."

American Gnosticism is an autonomy project -- it's all about us.  And it is that autonomy project on which adult contracting is based.  But it is loveless, irresponsible, and naïve -- a "permanently tentative and reversible commitment"⁴ giving no thought to children. 

Children are gifts, to be loved and cherished -- not acquisitions or abstract, optional, or discardable accessories.  McGill's Seana Segrue explains:

Where duty is subordinated to choice, or where adults are to be parents only to the extent that they choose to be parents rather than because they are mothers and fathers, children are placed at risk in a number of ways. The ability to choose to be a parent has as its corollary the ability to choose not to be a parent, or to abdicate responsibility where parenthood is not desired.

Morse highlights the problems:

First, contracts are limited, but parenthood is a status. Contracts are of limited duration, but parenthood is forever. Second, and more importantly, the child has been objectified. Instead of being a gift, the child is treated as a product or an object. ... Good intentions do not suffice to overcome the structural tendency for "contract parenthood" to objectify children far more often and deeply than natural parenthood.

... Biological parents, married to each other, have a great advantage: they both have a connection with the child. They've both got skin in the game, literally. When they are married to each other, they have made a commitment to work together to build a common life. The children are their common project.  This is not so for the child of an anonymous gamete donor.

Finally, the deepest reason why society has obligations to children is that this is the only position that is truly consistent with the idea that people deserve freedom, rights, and dignity in the first place.  Nature and Nature's God endowed us with certain inalienable rights[.]

Maccarini adds⁵:

[The] notion that the human being is created in the image of God is the foundation of the Western idea of freedom as a gift not from society or the state but from God himself. 

Children, as acquisition or lifestyle choice, are a fatal flaw of the contracting model.  Red flags are everywhere.  Consider: 

• The assumption of a "right" to children has resulted in fertility treatments, multiple embryos, and abortion so commonplace as to be euphemized as "selective reduction."
• No-fault divorce has doubled the divorce rate and devastated children.
• Check-the-box divorce forms have further decimated families.
• Most women having abortions (85%) do so outside traditional marriage.
• There is an increased incidence of attachment disorder and failure to thrive in children from foster care and orphanages, despite good-intentioned caregivers.
• Homosexual couples are 1.5 to 2.7 times as likely to break up as married heterosexual couples⁶.
• There is a more infidelity in committed homosexual relationships than in traditional marriages (and no, marriage is not a remedy for this weakness).
• Studies of gay mental health show more depression, alcoholism, sexual addiction, and sexually transmitted diseases, as well as higher risk of suicide, higher incidence of domestic violence/sexual abuse, and shorter caregiver lifespans. It is wrong to prescribe and dispense children as medicine for these ills.

It is self-gift, not autonomy or self-fulfillment, from which successful parenting springs.  Despite efforts to erase this fact, we know better.  Self-gift is achieved inside the other-oriented, childrearing institution of traditional marriage -- an institution still respected by most as more than sentimentalism or lust.  Nonetheless, Joe Biden recently had this to say:

Look, I just think that the good news is that as more and more Americans come to understand what this is all about, it's a simple proposition: Who do you love? Who do you love? And will you be loyal to the person you love? And that's what people are finding out, is what all marriages at their root are about, whether they're marriages of lesbians or gay men or heterosexuals.

The vice president is wrong.  Marriage is a unitive and procreative calling, and it is obvious that injecting more autonomy into marriage is a terrible idea and a contradiction.  James Schall comments⁷:

We are not a culture that never understood what a human being was in his nature and in his destiny.  Rather we are a culture that, having once known these things, has decided against living them or understanding them.  Indeed, we have decided to reject most of them, almost as an act of defiance -- as an act of pure humanism -- as if what we are is not first given to us.

It takes a family to raise a village, not a loose group of autonomously contracting adults.  Each step away from the traditional institution and toward a self-focused Gnostic personal affirmation is dangerous and likely to lead to the ditching of children, whether in or ex-utero.  As Morse says, "[i]t is not possible to create a free society in which everyone begins life as someone's choice."

Traditional marriage protects children.  Adult contracting redefines marriage to serve the needs of adults, resulting in instability, uncertainty, and impermanence -- all bad for a child.  The adult contracting model is an unjust dereliction of the duty owed to children as a result of its naïve, selfish, and Gnostic underpinnings.

¹Christian Europe?, Andrea Maccarini, First Things, May 2012, p. 53.

²Death on a Friday Afternoon, Richard John Neuhaus, Basic Books, 2000, pp. 117-120.

³Ibid.

⁴The Abolition of Marriage, Christopher Wolfe, Public Discourse -- Ethics, Law and the Common Good, May 2, 2011.

⁵Christian Europe?, Andrea Maccarini, First Things, May 2012, p. 53.

⁶Review of Research on Homosexual Parenting, Adoption and Foster Parenting, George A. Rekers, Ph.D., University of South Carolina, 2004.

⁷Josef Pieper, Leisure The Basis of Culture, Ignatius Press, Foreword 2009, p. 9.