>>1I personally don't think there's anything wrong with sex between two unmarried people, however when one or more of those people is married, it becomes more complicated, since you're violating a contract. I don't think the marriage contract really has to do with women being property (traditionally it was, in a sense, but modern marriages work "both ways" and limit the behavior of the husband as much as it does the wife), it's more that you've made a promise to have an exclusive relationship and shouldn't break that promise. If you're not really willing to only ever have sex with the person you're married to, it's probably better to get an open marriage than to make a promise you have no intention of keeping.