webdog said:
Good question. I'm not sure the converse can automatically be assumed, though.
Compare then:
Rom 7:2 For example, by law a married woman is bound to her husband as long as he is alive, but if her husband dies, she is released from the law of marriage. 3 So then, if she marries another man while her husband is still alive, she is called an adulteress. But if her husband dies, she is released from that law and is not an adulteress, even though she marries another man. (NIV)
Mt 19:9 And I say unto you, Whosoever shall put away his wife, except it be for fornication, and shall marry another, committeth adultery: and whoso marrieth her which is put away doth commit adultery. (KJV)
These verses are similar but in reverse gender. The reason vs. 9 is adultery is because he is still married to the first wife in God's eyes. From vs. 6 in Matthew
What therefore God hath joined together, let not man put asunder, (not the lawyer, not the judge, not even oneself), we see that the marriage is still in effect in Gods eyes. The first is his wife; the second is his partner in adultery. (the same as Rom 7:2,3
So taking another wife, in the absence divorce for fornication or death constitutes adultery. Therefore polygamy equals adultery.