Most people who stubbornly cling to the monogamy-only position refuse to discuss the topic with someone who, like the author of this post, believes that it is not a sin for a man to have more than one wife. But if one can actually get into a discussion with such a person, it will not be long before the monogamy-only advocate retreats to this fallback position:
God’s ideal plan for marriage is monogamy, because He only created one wife for Adam.
That statement makes an illogical leap from a biblical truth (God created only one wife for Adam) to an unwarranted conclusion (therefore, God’s ideal plan for marriage is monogamy). But, just for the sake of argument, let’s pretend that the stated biblical truth actually warrants the conclusion. Then, if we are to be consistent hermeneutically,1 there are at least two other very obvious things in the first three chapters of Genesis to which we must apply the same rule of interpretation:
After Adam sinned, he and Eve made garments from vegetable matter. (Fig leaves; Genesis 3:7).2 But God made garments for the couple using animal skins, replacing the vegetation they had sewn together with garments that required the shedding of blood in order to make them (Genesis 3:21), showing that anything that does not require an animal to bleed and die is less than God’s ideal plan for material to be used when making our clothing. Therefore, just as a man should have only one wife, we should only wear clothes that are made from animal skins.
Adam was told by God that he was to be a gardener (Genesis 2:15). Adam was also told that his task of gardening would be more difficult because of the curse (Genesis 3:17-19), which shows that Adam’s job assignment was not changed from gardener to something else after they were expelled from the Garden of Eden. Therefore, just as a man should have only one wife and we should only wear clothing made from animal skins, all men should be gardeners. Any other occupation is less than God’s ideal plan for man’s employment.
In actuality, of course, we cannot derive spiritual or moral laws solely from examples. God always explicitly tells us what He considers to be sin and what He requires of us. (For example, the Decalogue gives us ten of His explicitly stated laws.)3 Yes, He does give us examples in many cases, but He never gives us an example of something He wants us to do or not do without very plainly telling us that whatever the example depicts is a one of His laws. That law might be recorded much later in Scripture, but it is there somewhere if the example is an example of one of His laws. Cain was punished for killing his brother Abel (Genesis 4:1-16), but we are not explicitly told that murder is sin until Genesis 9:6, after the Deluge has subsided enough that Noah and his family (and the animals, of course) can leave the Ark.
1 For the definition of hermeneutically, see http://www.webster-dictionary.org/definition/Hermeneutically.
2 Unless otherwise noted, all biblical passages referenced are in the King James Version.
3 The Decalogue, known colloquially as The Ten Commandments, is found in both Exodus 20:3-17 and Deuteronomy 5:7-21.