For most people their ideal life involves an intimate relationship with another person; one which often has a sexual basis. But there's no logic about it; why shouldn't people choose to live together with someone they just like? 'Of course' if we were too unquestioning about it, and we said 'well, that person has got to be someone of the opposite sex, and it's got to be for life, and divorce is terrible', then we're stuck. But if you don't recognize the importance that kind of bond has for human beings - you can't really understand what is needed to live a good life.