The widespread acceptance of contraception leads to the widespread acceptance of same-sex marriage, whether wittingly or not. All of us who justify the use of contraception are responsible for creating the very logic (mentality) that justifies extending marriage to same-sex partners.
The purpose of contraception is to render a fertile act of sex sterile. Using contraception always includes a willful act to separate sexual activity from babies. Implicit here is the belief that sexual union can be an authentic expression of love even when the couple does something to sterilize their act(s) of sexual union. In theological terms, it is the belief that we can separate the unitive and procreative ends of sex: i.e., that we can have the one without the other.
No matter what side of the marriage debate we’re on, we all agree that marriage necessarily involves sexual union. What distinguishes conjugal love from every other form of love—e.g., paternal, maternal, filial, friendship—is that conjugal love is expressed and sealed through sexual union.
If, however, we believe—as in the contraceptive mentality—that sexual union can be an authentic expression of love without also including the openness to life, then babies are seen to be extrinsic rather than intrinsic to marriage. Openness to procreation, then, does not belong to the very substance and definition of marriage. It is merely an option for those couples who happen to want children.
This idea, however, opens wide the door to extending marriage to same-sex partners. Indeed, it provides the very logic that justifies this form of “marriage.” Same-sex sexual activity is inherently not open to procreation. Their sexual activity is the kind of activity that is, by its very nature, non-procreative.
Yet, if we accept the notion that sexual activity which is not open to procreation can be an authentic expression of conjugal love and that openness to procreation does not belong to the very essence and definition of marriage, what is the possible rational basis for not extending marriage to same-sex couples? There is none, because marriage has been reduced simply to a loving, committed sexual relationship.
Some might object: if openness to procreation belongs to the very essence and definition of marriage, we would have to exclude not only same-sex partners from marriage, but infertile heterosexual couples as well. This objection is not valid and does not hold weight. The sexual activity of an infertile heterosexual couple is intrinsically open to procreation—even though their sexual union cannot result in procreation. The sexual act of an infertile couple is the kind of act that is open to procreation; the fact that it cannot lead to procreation is accidental to the act itself. Under normal circumstances—i.e., functioning fertility—their act could lead to procreation. On the other hand, the sexual act of a same-sex couple is the kind of act that is never open to procreation; the non-openness to procreation belongs to the very substance and essence of that act.
Thus, one can rationally hold that openness to life is intrinsic to conjugal love without excluding infertile couples from marriage. Infertile heterosexual couples engage in the kind of act that leads to procreation; homosexual couples do not.
Blessed John Paul II was prophetic when he wrote the following in Familiaris Consortio:
[T]heological reflection is able to perceive and is called to study further the difference, both anthropological and moral, between contraception and recourse to the rhythm of the cycle: it is a difference which is much wider and deeper than is usually thought, one which involves in the final analysis two irreconcilable concepts of the human person and of human sexuality.
We might add that the difference, both anthropological and moral, between heterosexual and same-sex marriage is also one which “involves in the final analysis two irreconcilable concepts of the human person and of human sexuality,” as well.