This thesis follows from the arguments in thesis 1 and from my understanding that laws or other regulations banning a certain behavior may be imposed only to prevent harm (see thesis 3). As stated in thesis 1, the legally effective authorization of multiple relationships, whether in the form of polyamory or polygamy, would not create any damage, neither to individuals nor to the society.
On the contrary the admission of multiple relationships might help to prevent a lot of unnecessary damage, in particular many divorces stemming from sexual infidelity could be avoided. Instead, there would be more durable marriages and families. These polygamous families would probably have more offspring and provide a stable family environment over a longer term than the monogamous marriages, which in western societies mostly divorve after 5 years. In my article Evidence-based policy would mean to legalize polygamy, I point out that policy – if it were based on evidence – would have to realize that monogamous marriage as the only and by law coercively enforced model for long-lasting relationships is not working for most people and needs to be supplemented by other options.
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