A: "In sexual activity, as in all other forms of human interaction, LOVE must be the rule of living, as Jesus has said. Jesus exhorted us to always do nothing to others that we would not want done to us, and more positively, to do unto others that which you desire others to do to you. In the sexual union, one would want to have mutuality of consent, and loving intentions above all. As long as there is that bond of love (ideally that of marriage or commitment), and a mutual desire, then there would certainly be room for a good bit of "liberality." What that might mean would have to be determined by the parties involved.
It seems to me that any activity, including sexual activity, becomes sinful only when it violates this rule—when it is purely selfish, or when it is harmful to another, either mentally, physically, or spiritually. And of course, if one persists in selfish or hurtful ways, then such activity would eventually meet the requirements of iniquity.
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Thanks for this important question."