There are some situations in which it is advantageous to society to have men marry multiple wives, and for this reason polygyny is practiced by many religions and cultures. As we have already seen in answer to question 2, polygyny is permitted in the Bible too. Here we will see that the Qur'an permits only a restricted and limited form of that practice. Only 2% of Muslim marriages are of this nature.

Notice that the Qur'an permits but does not command a man to have four wives. Furthermore, the Qur'an stipulates that a man is responsible for the maintenance of his wife or wives. If a man has more than one wife, he has to provide separate living accommodation for each of his wives. Multiple marriages are a heavy responsibility on the male. It is not a pleasure trip as some people may assume. Some even imagine all kinds of sexual exploits involving a man and his wives altogether. However, such activity is not permissible in Islam. A man must divide his time equally among his wives. He may, for example, spend one night with each wife on a rotating schedule. If a man cannot maintain justice in the treatment of his wives, the Qur'an stipulates that he is to have no more than one wife.

Polygyny provides a solution to some of life's problems. When there is a shortage of men, for example after a devastating war, many women will be unable to find husbands. Most women in that situation, given the option, would rather be a co-wife than no wife. If one maintains a strict monogamy in such a situation, moral depravity is bound to result.

It may be useful at this point to see what some non- Muslim writers are now saying on this much misunderstood subject. John Esposito says:
Although it is found in many religious and cultural traditions, polygamy (or more precisely, polygyny) is most often identified with Islam in the minds of Westerners. In fact, the Qur'an and Islamic Law sought to control and regulate the number of spouses rather than give free license. (John Esposito, Islam: The Straight Path, Oxford University, 1988, p.97).

Esposito then goes on to explain that in a society which allowed men an unlimited number of wives, Islam limited the number of wives to four. Then he continued to say:
The Qur'an permits a man to marry up to four wives, provided he can support and treat them all equally. Muslims regard this Qur'anic command as strengthening the status of women and the family for it sought to ensure the welfare of single women and widows in a society whose male population was diminished by warfare, and to curb unrestricted polygamy (John Esposito: Islam the Straight Path, p.97).

Karen Armstrong explains much the same in her book entitled Muhammad: A Western Attempt to Understand Islam. She says:
We have to see the ruling about polygamy in context. In seventh-century Arabia, when a man could have as many wives as he chose, to prescribe only four was a limitation, not a license to new oppression (Karen Armstrong, Muhammad: A Western Attempt to Understand Islam, Victor Gollancz Ltd., 1991, p.191).

It is unfortunate that the Western media often gives the wrong impression of what Islam is all about. Karen Armstrong writes:
Popular films like Harem give an absurd and inflated picture of the sexual life of the Muslim sheikh which reveals more about Western fantasy than it does about the reality (p.190).

Some people incorrectly assume that because of this ruling most Muslim men would have four wives. However, as Huston Smith points out, "multiple wives are seldom found in Islam today" (The World's Religions, p. 252). Ira Zep p, Jr. says that "less than 2% of Muslim marriages are polygamous" (A Muslim Primer, p.180).

About this being a solution for the problem of surplus women, Ira Zepp, Jr. comments on page 181 of his book:
The Roman Catholic Church is facing the same problem today in parts of Africa. Social and economic reasons are forcing the Church to reconsider polygamy as a Christian option. (See Polygamy Recon,isidered by Eugene Hillman, New York: Orbis Press, 1973).