Rob Hughes, a young moral, political and legal philosopher teaching in the Wharton School at the University of Pennslyvania, writes:
Having read Richard Swinburne's recent argument about the ethics of homosexuality, both the version he published in 2007/2008 and the version he presented in his talk at the SCP meeting, I can confirm your belief that his argument is awful. There is no need to discuss Swinburne's dubious moral premises. The argument clearly fails because it relies on a false and unjustified empirical assertion. Here it is, in Swinburne's own words (from the text of his recent talk posted on First Things, pp. 12-13):
"The evidence seems to me to indicate clearly that genes and environment (nature and nurture) both play a role in determining sexual orientation; and also that this orientation is sometimes to a considerable extent reversible. So if there was a general recognition in society of an obligation to abstain from homosexual acts, that would prevent homosexual behaviour being presented as an option for young people of equal value to the heterosexual one which makes possible procreative marriage. That would deter the young from wondering whether they are really homosexual when previously it would not have occurred to them, in consequence experimenting with homosexual sexual acts, getting accustomed to such behaviour and so developing a homosexual orientation."
Swinburne asserts here that sexual experimentation in adolescence or adulthood influences people's sexual orientation. This assertion is not an off-hand remark; it is crucial to his argument that God has a reason to prohibit homosexual conduct. (Swinburne does not think that natural law prohibits homosexual conduct; indeed, he nicely dispatches this view in one sentence on p. 8.) Swinburne's assertion is at odds with the evidence that a person's future sexual orientation is determined before school age and possibly much earlier. He provides no evidence for his assertion that sexual experimentation influences orientation, either in his 2007 book Revelation, or in his 2008 reply to critics, or in the text of his recent talk.
Swinburne claims to have provided evidence that adults can change their sexual orientation, but to call his evidence shoddy would be too generous. His 2007 book cited a study purporting to show that some people had changed their sexual orientation through "reparative therapy." The study's author, Robert Spitzer, retracted the study in 2012 and said that its methodology had a "fatal flaw." Swinburne's recent SCP talk acknowledges this retraction. The talk instead cites Michelle Wolkomir's 2006 book Be Not Deceived as evidence that "the sexual orientation of some, but perhaps not most, homosexuals can be changed to a significant degree." (19) The book is an ethnographic study of two small groups of gay and "ex-gay" Christians and their self-understanding. Treating this study as evidence that people can change their sexual orientation is a mistake for the same reason Spitzer's study was flawed: we have no way to establish that subjects who reported changed sexual desires were sincere and not deceiving themselves. The large number of ex-ex-gays gives us reason to suspect that people are either insincere or deceiving themselves if they claim to have altered their sexual orientations (including their desires as well as their behavior).