text: why is bigamy/polygamy illegal? if a man has the material means and desire to support two or more families, and the families are agreeable to sharing the husband, why is it wrong? isn't it better for the man to care for his extra family rather than throw them aside? (for that matter, why shouldn't a woman have two or more husbands?) please do not quote any religious texts or cite morality as the reason. i want to know legally why it shouldn't happen. the legal reason is because it is against the law.   the question of why it is against the law cannot be answered if you do not let the answerer cite moral or religious reasons -- most criminal statutes and many civil statutes are ultikately based or moral reasons, and morality for many has ties to religion.  there are policy reasons which go beyond simple moral reasons -- the laws of our society (laws of property ownership, inheritance, parental rights, marital property, etc.) are structured on the assumption that only two people are involved in a marriage.  allowing plural marriage creates situations which the law cannot handle.    there are also more sociological reasons -- in practice, much plural marriage occurs when the women are very young, and it might reasonably be determined that exploitation and coercion are involved more often than free choice.    but morality is behind all questions of "should" or "should not."