Thus, it is the procreation and upbringing of children that makes marriage such a social good. The state accordingly invests in marriage between a man and a woman because it knows that it is the ideal and best possible method of insuring its future through the procreation and education of children.
Indeed, traditional marriage is so fecund that those who would frustrate its end must do violence to nature to prevent the birth of children by using contraception. The natural state of marriage is to produce not only children but many children to populate the state.
On the contrary, same-sex unions are so sterile that those who would circumvent nature must employ costly and artificial means or employ surrogates to bring about adoptive children. The natural state of such unions is not to produce any children, much less many children.
Such unions therefore fail to fulfill marriage’s social good since most simply have no interest in either procreating or employing costly artificial substitutes.
Again, the state knows that marriage between a man and a woman is the best possible means of insuring this goal which benefits the common good. Historically, the State has invested heavily in insuring this bond.
The reasons are many. First the children of such unions are normally the flesh and blood of both parents who see their offspring as extensions of themselves. Such unions provide a father and a mother, complimentary role models that perform different functions in child development. The children also can have the added intense affection of numerous siblings of those same parents.
The parties of traditional marriage make a life-long commitment to maintain this bond to provide a stable atmosphere for the children to develop. Moreover, they agree to exercise moral restraint and fidelity to their marriage vows to prevent outside elements from interfering in their union and thus disturb the moral well-being of their offspring.
The experience of centuries gives irrefutable testimony as to how these blood relationships inside a stable moral climate naturally lead to affection and the creation of the best possible conditions for the upbringing of children.
tfp.org/tfc/1049_reasons_to_oppose_same-sex_%5Emarriage%5E.htm