While it is true that
polygamy is allowed in Islam, it is nevertheless deeply misunderstood to those outside the
religion. Islam institutes
polygamy under very strict guidelines and even then the conditions for maintaining a polygamous marriage are very
strict in and of themselves.
The reason for the advent of Polygamy at all in Islam comes down to warfare and the inevitable result of sending large parts of the strong healthy male population in society to engage in the dangerous task of fighting in a war. The results more often than not, is death, and many families are left without men. Naturally women can fight in war as well as men, the choice is theirs, but it is also a fact that when faced with the choice, less women choose to engage in warfare than men, for whatever reasons that may be. Anyway, the consequence of all of this is that, supposing the Islamic society wins, there is a shortage of healthy males of a marriagable age.
Now while this may not be much of an issue today, back in the days before the welfare state, and women's lib, it was the man who gave a woman and her family a place in society, and more importantly, who provided the money and food. Without men, women suffered, as they often could not match the incomes of their dead husbands when they started working to pay for their childrens growth. So for this reason the Prophet allowed more than one woman to be married to a man.
However, like all such matters of the heart, these things are prone to make people vunerable, and so strict conditions must be met before the marriage and also during the marriage for anyone contemplating a polygamous lifestyle.
Firstly, and most importantly, he must have the free consent of his current wife (or wives), and also the woman that is about to be married should know be okay with the fact that there is another wife already there. This is crucial. There can be no deception in this.
Secondly , He must treat all wives equally. This isn't quite as easy as it sounds, nor is it vague enough so that the man can skirt around his duties. He must provide each woman her own house/living quarters, he must share all the gifts of his wealth and knowledge and personality equally between them (ie no favourites),
Thirdly - he must spend an equal amount of time with each of them.
Fourthly - He must be economically capable of looking after each wife and the kids should they come along.
And Finally he is only allowed up to 4 wives.