The writer of Proverbs includes on the list of things “too wonderful” to understand this intriguing item: “the way of a man with a maiden” (Prv 30:19).  The biblical view of human sexuality affirms that it is indeed in many ways a mystery to be marveled at.  Despite the mystery, however, the Catholic Church affirms that certain essential truths about our sexual nature have been revealed to us by God, our Creator.

With regard to homosexual behavior, the Catechism (2357) teaches:

Basing itself on sacred Scripture, which presents homosexual acts as acts of great depravity (cf. Gn 19:1-29; Rom 1:24-27; 1 Cor 6:10; 1 Tm 1:10), tradition has always declared that “homosexual acts are intrinsically disordered” (CDF, Persona Humana 8).  They are contrary to the natural law.  They close the sexual act to the gift of life.  They do not proceed from a genuine affective and sexual complementarity.  Under no circumstances can they be approved.

With regard to homosexual orientation, the Catechism (2358-2359) continues:

The number of men and women who have deep-seated homosexual tendencies is not negligible.  This inclination, which is objectively disordered, constitutes for most of them a trial.  They must be accepted with respect, compassion, and sensitivity.  Every sign of unjust discrimination in their regard should be avoided.  These persons are called to fulfill God’s will in their lives and, if they are Christians, to unite to the sacrifice of the Lord’s Cross the difficulties they may encounter from their condition.

Homosexual persons are called to chastity.  By the virtues of self-mastery that teach them inner freedom, at times by the support of disinterested friendship, by prayer and sacramental grace, they can and should gradually and resolutely approach Christian perfection.

Given these truths, a homosexual union can never be equivalent to marriage.  God has naturally structured human sexuality to make man and woman complementary partners in transmitting life.  This sexual complementarity can only be expressed by the union of male and female, which makes possible the conjugal bond at the heart of marriage (see Gn 1:27-28; 2:18-24).  Same-sex union is thus contrary to the very nature of marriage.

Related Scripture:

Texts Cited:  Gn 1:27-28; 2:18-24; 19:1-29  •  Prv 30:18-19  •  Rom 1:24-27  •  1 Cor 6:10  •  1 Tm 1:10
General:  Mt 11:23-24; 16:24-25  •  Phil 3:8-11
Catechism of the Catholic Church:  369-372  •  383  •  1605  •  2331-2363  •  2392-2396  •  2520-2527  •  2529-2533