A homosexual tendency is an exclusive or predominant inclination towards same-sex attraction. It's the opposite of a normal heterosexual tendency of being sexually attracted to persons of the other sex. The tendency or inclination towards same-sex attraction becomes sinful if acted upon.
The practice of homosexuality, insofar as it involves committing homosexual acts, represents "grave depravity," as taught by the Catechism of the Catholic Church (CCC) in paragraph 2357. The CCC teaches that a homosexual act is "intrinsically disordered" because it's an unnatural use of the sexual gift. It's not a conjugal act that manifests sexual complementarity but is, rather, a type of mutual masturbation.
The CCC in paragraph 2358 teaches that an "inclination" towards same-sex attraction is "objectively disordered" because it leads to an intrinsically evil homosexual act instead of a natural act of conjugal sex within marriage and open to procreation. The CCC further teaches that the subjective feelings based on homosexual desires "do not proceed from a genuine affective and sexual complementarity." This means that without sexual complementarity, homosexual acts are devoid of life and love.
When a sexual act is not open to procreation, it is not an expression of genuine or authentic love. Pope St. John Paul II made this point when speaking of contraceptive sex in his 1984 commentary on the papal encyclical Humanae Vitae (1968). In paragraph six, John Paul II writes, "[T]he conjugal act ... artificially deprived of its procreative capacity, ceases also to be an act of love."
In paragraph 2358, the CCC emphasizes that a homosexual inclination in people "constitutes for most of them a trial." It adds that Christians with a tendency towards same-sex attraction are called "to unite to the sacrifice of the Lord's Cross the difficulties they may encounter from their condition." This means that people who struggle with same-sex attraction can become holy by co-operating with Christ in resisting such temptations.
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