Whether homosexuality is a sin has become a topic of hot theological debate among Christians in the half century since World War II. Many liberal Christians are moving towards a view that no longer considers homosexuality to be a sin, while many others retain the traditional Christian view, which holds that homosexuality is a grave sin. Among protestants, this traditional view is generally strongest in the US, while American catholics are typically more liberal than catholics elsewhere.
Prior to the twentieth century, most Christian teaching has held that homosexual behavior is a sin, based on such Biblical passages as Leviticus 18:22 ("You shall not lie with a male as with a woman; it is an abomination."). Romans chapter 1, and the Ten Commandments prohibition on adultery, and other verses have traditionally been understood to prohibit any sexual activity that is not between husband and wife (see Fornication).
The Christian theological arguments against homosexual acts rest chiefly on the specific verses held to prohibit the act, as well as the general restriction of all sexual activity to that between husband and wife.
Many traditionalists view homosexual behavior as a freely made choice, and believe that it is possible and desirable to transition to heterosexuality. This view is strongly rejected by most psychologists.
Liberal Christian theologians who do not believe homosexuality to be a sin argue that the traditionalists have misinterpreted the pertinent Bible passages or quoted them selectively. For example, they consider the original Hebrew in Leviticus to be ambiguous as to whether "male" means adult man or boy. The fact that Leviticus prohibits several activities that are nowadays accepted, such as shaving, is also sometimes presented as a counter-argument. Similar critiques are made of other verses.
Rather than interpreting the term "adultery" in the Ten Commandments to mean any sex outside of marriage, they interpret it to mean sex with somebody else's spouse, which then makes it irrelevant to homosexual relationships.
Modernists generally argue that homosexual desires are present in a person at birth (a position for which scientific research has provided some evidence, although not yet conclusive proof) or in early childhood. They further argue that to deny people the right to express romantic love with another human being in the manner that God endowed them with is not an act of compassionate love. Many theologically liberal Christians agree and believe that God wishes the person to fulfill these inborn desires.
Positions of specific churches
The Roman Catholic Church still considers homosexual behavior a sin, but has clearly stated that homosexual desire itself is not. Other prominent figures outside the Catholic Church, such as the Episcopalian bishop John Spong, have argued extensively in favor of the view that homosexual behavior is not a sin.
Unitarian Universalists do not believe homosexuality to be a sin. They ordain gay and lesbian ministers, and welcome gay people into their congregations both informally and formally.